psstein

Once I got to intermediate proficiency, reading newspapers in my research languages first thing in the morning was very helpful.

One more tip: advanced readers are rare but they do exist. Depending on the language, Dunwoody Press (which was dead for a long time and is now reviving its old glory) published many such readers for laughably less-taught languages. Since many of these books are out of print, it is worthwhile to search on WorldCat or your university library catalog. If you are already quite acquainted with the grammar, even a reader whose auxiliary language is other than English (the Soviets were good in publishing readers) can be useful for you -- you just need graded, well-chosen texts for your practice. Searching for old textbooks is also a gem because it helps you ease into reading primary sources. It is funny, perhaps, but reading what an American/British learner of German read to study German in the 19th century is actually quite useful in the post-beginner stage.

Before you try to go the PhD route, ask yourself what it is you want out the PhD. The academic job market has been abysmal for years and currently non existent. The state of academia and higher ed is a complete disaster and chances are almost zero anything will change in the next few years. It's almost certain that you will not get a tenure track job, so if that is your goal, I urge you to reconsider and NOT do a PhD. If that is NOT your goal, then why do a PhD? If you just want to learn things, you can do that without going through the arduous and often demoralizing process of getting a PhD only to end up less qualified for non-academic jobs than you were before going in. If you are independently wealthy and just want to do a PhD for fun, I question your definition of fun, but go right ahead.
Museum curators have their own career path and a PhD in History is NOT the best way to go about it. Plus, they have their own job market issues. If you want to be a curator, look into Public History programs with a museum specialization, or into a Museum Studies program.
Also, absolutely do not attend a PhD program that does not cover your tuition AND gives you a stipend.

Congrats on this unofficial offer.  I'd se what the funding package looks like.  I would ALSO communicate that you have a full funding offer to attend Oxford for a year and see how they react.  $17K is definitely UNLIVABLE in the SF Bay Area. $28K is pushing it, but I'd consult the funding spreadsheet to see if that's typical.

Don't worry.  Wait until after April 15th.  You'll usually be given a little time to accept the offer if they make it to you then.
 
@bakesealactually, having a full-funded studentship at Oxford is a *very* big deal and possibly just as good as getting a PhD acceptance at Berkeley. Had you gotten into Berkeley, I would have advised you to defer your admissions if you could and take advantage of this studentship. (I actually had to explain to my non-academic family that my cousin's funding for Cambridge was like winning a lottery and should be celebrated. Not just "oh, that's nice that they got merit aid.")  *Everyone* knows that when reading your CV for applications of any kind going forward. CONGRATS!!!

This is bodes *really* well for your next cycle. Head up.

I got off the William & Mary waitlist today. Best of luck to you with the Harvard waitlist, and to all of the waitlisted folks out there! ?

IDK if this standard is realistic. Who among us has not had those moments when we're sure that either we and/or the person who wrote a well received work doesn't know WTF history is about? 
@apotteba, I would suggest that you understand that it's going to take thousands of hours of work to get to the point where you understand history well enough to spend thousands of hours more work to create new knowledge. Along the way, you will face make or break tasks. Throughout, you will be competing for resources, funding, and support against other aspiring historians--some of whom will have been majoring in history since middle school.
IRT your opportunity this summer, I recommend that you visit the websites of highly regarded history departments to see if you can find documents related to the preparation of an undergraduate thesis or honors thesis. (To get you started, here's a link for Happyland University's senior essay.)
When it comes to developing a topic, I recommend that you ask yourself (at least) three questions simultaneously:
What topic/field/area/time period do you want to write about? What primary source materials are available? [I seriously screwed up on this one when I picked my dissertation topic.] What is the state of the historiographical debates?  Understanding these debates is crucial because they will help you develop the specific questions and controversies you want your paper to address. Concurrently, I recommend that you develop reading lists that help you to understand the following questions:
What is history? What is historiography? Why is the study of history important today? [This is a trick question.] What is the "state of the art" of your area[s] of interest? How did the most accomplished and respected practitioners in your fields of interest develop their skills as historians? (@AfricanusCrowther's recommendations are right as rain, this post is meant to serve as a rain jacket.)
At the same time:
Start a journal (analog or digital) in which you start jotting down your questions / thoughts / theories about history. Use the journal to develop your writing skills as a historian. Obtain this style manual .  IRT your stated interests, try to imagine questions and themes that may link them together and from there generate questions and imagine themes that may take you further along the path or towards different paths. (Just spit balling, how about a comparative study of how film was used to alter configurations of power in Russia and Columbia at either the same time or under the same conditions (examples include the efforts of the U.S. to expand its power in the Western Hemisphere and Eastern Europe. 
ETA:
Something to keep in mind, COVID-19 has underscored the extent to which academics and other professionals in the Ivory Tower don't know how to read a balance sheet, much less decipher it. And at the same time, academic history remains a profession in crisis.

How about using your accounting skills to prepare a research paper that is essentially an audit of the AHA?  Your source materials would include the documents available here. You could evaluate the financial performance of the AHA against KPI identified, if not clearly defined, by the association itself. You could also compare the AHA to other professional organizations (history and/or other disciplines). You could also discuss the way the AHA and other organizations have used data the last couple of decades -- do these uses reflect the best practices of professional accountants?
 

I know this isn't the advice you want to hear, but PLEASE consider using your accounting degree to its fullest extent. Your chances of secure, long-term employment with that degree are drastically better than those chances (especially in academia) after earning a history PhD.
As @AfricanusCrowther hinted, the academic job market is in disarray from COVID-19, but has gotten progressively worse since 2008.
Also, bluntly, I think you're too far behind the eight ball here. The only thing you really have going for you is your knowledge of Spanish. Outside of that, without a clear research agenda or well-developed skills, you're not going to have an easy time getting into a program worth attending.
With all that said, if you want to make your way towards a history PhD, I'd suggest reading the major journals of the field and looking into the possibility of a part-time MA. I know many programs offer them.

Can you provide additional information about what this "summer research institute" will entail?
You have your work cut out for you. Most people will think that the ship has sailed. IMHO, the most important thing you can do right now is figure out what sorts of questions historians answer, what kinds of claims they make, and how they use evidence to support their claims. Being an academic means contributing to the production of historical knowledge and pushing debates within the field. Read academic history journals (I'd start with the American Historical Review, the Hispanic American Historical Review, and maybe other journals related to your interests in economics and film). Read The Craft of Research. Read an introduction to contemporary historical thought, like Sara Maza's Thinking About History. Then try to write research papers that replicate what you see in a smaller scale. If none of your classes assigns a research paper, ask one of your professors if you can write one as an optional assignment.
Part of this work will be learning that history is a massive field that comprises an overwhelming number of methodologies and theoretical approaches. If you wish to pursue history on the graduate level, you will need to identify which methods and theories inspire you the most and are most helpful for answering your burning questions about history and historiography.
Only when you really understand what academic history is about -- the language that it speaks, the knowledge that it creates, its terms of argumentation -- should you consider master's programs. And you should look for a program where tuition is free. Don't take on debt.
The problem with academic history as a profession is not the "pay," but the scarce supply of good jobs.

I think the prestige difference between the degrees, even if there was any, would be the least important bit in your application. 

IDK, if they roast you for trying, then that's really good information to have early.

It may be worth it, but in an age of belt-tightening and an even more uncertain future for the humanities, you may give the wrong impression to people who can and will make life difficult for you.  You're incredibly fortunate to have funded offers, considering the cycle's competitiveness and the large number of quality programs who refused to admit new cohorts.

I'm so sorry you're going through this. Rejection is a huge part of academia, but it doesn't mean the sting goes away. Your value isn't tied to an acceptance to a PhD program. I recognize saying that is easy, and feeling the truth of it is much harder in these moments.
It is brutal in the humanities right now. Absolutely brutal. And we haven't felt the full impact of it yet. Rejection now can be an opportunity for you to reassess if it's worth it when the number of jobs is becoming vanishingly small--and the number was small pre-covid. I started my program in 2015 fully understanding the challenges and accepting the risk. A sad realization I've had over the past year is, if I had to apply today facing the post-covid market, I wouldn't. I also wouldn't accumulate debt to get an MA when even the programs with good placement records are going to struggle to place their grads in academic jobs. But it's an individual choice. As always, each prospective and current grad student needs to assess the risks themselves.

Bear in mind too that even those schools that do hire a lot of PHDs will still desire applicants who appreciate that college teaching and high school teaching are not the same (or so I've heard). When you get to graduate school, talk to the people (faculty or grad students, as the case may be) running the professionalization program in your department to see if you can organize a panel or two on high school teaching featuring those who have made the transition.

You might want to consider teaching in private schools/prep schools that do generally prefer PhDs. Take a look and see what the qualifications are.  Also you'll want to think about where you'll ultimately want to teach high school -- most states require certification for teaching, which is *not* part of any PhD teaching training and is something you'll have to do on your own on the side.

A few statements here:
1) There are zero programs worth attending that do not offer funding. Given the nature of the academic job market, I'd consider an unfunded offer a soft rejection.
2) I don't have enough understanding of your particular field to give good answers regarding programs you should consider.
What I would suggest is to look at the books you found compelling in your respective areas of interest. See where the authors work and where they received their PhDs. Then, look at the citations. Who's being cited most frequently? Where do these scholars work?
 

I agree with what psstein said about funding. On paper, you sound like a fine candidate, but PhD admissions in history mostly come down to the quality of your written work, especially the strength of your statement of purpose, and how well a department would serve your research interests ("the fit").
In terms of finding programs, think about the important books and articles published on the topics that you want to research and find out where those people are teaching. Then get a sense of how many successful PhD candidates those programs produce. If in doubt, consult Google Scholar.
It's great that you might want to teach high school, but make sure to plan for this potential career path while in grad school. There are steps you can take that will make the transition to high school teaching much smoother.

A few statements here:
1) There are zero programs worth attending that do not offer funding. Given the nature of the academic job market, I'd consider an unfunded offer a soft rejection.
2) I don't have enough understanding of your particular field to give good answers regarding programs you should consider.
What I would suggest is to look at the books you found compelling in your respective areas of interest. See where the authors work and where they received their PhDs. Then, look at the citations. Who's being cited most frequently? Where do these scholars work?
 

On top of what others have said, I hope I had asked more about the institutional support for professional training and development (as opposed to the intellectual training), and you can probably also gauge people's interests in/open-mindedness about those matters through the conversation. 
For instance, what if I want to learn how to do digital humanities (e.g. historical GIS, Python, or statistical analysis)? What if I want to get systematically trained in pedagogy (as in going through a program to get a certificate and create a portfolio that involves multi-year commitment and effort)? What are the opportunities and (funding and other) support if I want to propose and organize a workshop? Are there professional duties/services expected of me, e.g. chairing a graduate studies groups for a year or more, or serving on some committees?
I personally find the experience of performing professional duties/community services, such as organizing events/workshops with invited speakers, very practical and helpful, especially in terms of learning how to navigate the logistics, e.g. "oh gosh all the nitty-gritty that can possibly go wrong! (and the tax exempt forms!)" 
 
 
I heard drastically different descriptions of my advisor's mentoring style before starting my program, and ended up asking mine about it directly. It turns out my advisor is more than happy to adjust their advising style to students' different needs and styles. (I am the type of students who wants to have at least weekly discussions with their advisor; but I know my case isn't necessarily common.) So, if there are no red flags, stay a bit of open-minded until you know your advisor(s) more might not be too bad an idea!

I came straight out of undergrad, so I didn't really know what to ask. You should try to get a sense of your advisor's advising style (e.g. very engaged, laissez-faire, or somewhere in the middle?).

I came straight out of undergrad, so I didn't really know what to ask. You should try to get a sense of your advisor's advising style (e.g. very engaged, laissez-faire, or somewhere in the middle?).

Ask about living expenses, funding opportunities for conference and research travels. Ask if their 9-month stipend is livable for 12 months (spoiler alert: most grad students don't think about stretching their 9 month payments over 12 months). Ask about summer support.  Ask about unexpected expenses of attending that PhD program.
Also, ask about how easy it is to get mental health support.

Additionally, ask about fees. While programs cover tuition, there are usually some fees (mine amounted to about $250 even during the summer, because you had be registered to get paid. We got paid one month during the summer). 
As faculty now, the "best" questions are usually the ones that make me talk, like what's my favorite thing about the program, the school, or students; what opportunities I had to mentor students (I'm a recent hire, obviously), where have I encountered other grad students outside of our program. Usually like talking about things that make them proud

Yeah, this was my approach as well. I rarely take notes during a class, unless it's some particularly insightful point someone made or I want to say something down the road.
@historygeek, I'd recommend reading with a heuristic tool called IPSO. It stands for Issue, Position, Support, and Outcome. I stole it from my friend, who uses it for reading/teaching. It's very useful for teaching undergrads how to break down a piece of dense writing into its constituent parts. It works like this?
Issue: What is the research question? What is the author examining?
Position: What is his/her argument or thesis statement?
Support: What evidence does the author use to support the thesis? This includes not only data points, but secondary source scaffolding.
Outcome: So what? If we accept the author's argument, what are the other avenues for research?
I do realize that this framework seems a bit reductive and simplistic, but trust me, it's really helpful when you're reading scholarship that submerges the ideas. In my own field, it's helped me demystify Latour and Simon Schaffer.