Hey Juno,
I was also lucky in that I had a friend go through this whole process the year before I did so she was a great source of advice and encouragement for me!
Let me try to answer some of your questions...
I can't say for sure but my feeling is that my extra-curricular stuff made my application more appealing. The journal sounds great! I would definitely mention that in my application if I was in your position, and your other stuff will make you appear a more dynamic, hard-working and well-rounded applicant.
As for money, I didn't apply for any scholarships for studying in the US. You'll find that many external funding opportunities are for US applicants/citizens only. However, I made sure I applied to programs that offered tuition waivers and generous stipends as part of their admissions offer. This info is usually on departmental homepages, and when I couldn't find it online, I emailed grad program coordinators for the info. MAs in the US are sometimes funded but rarely are they funded enough to cover your international tuition plus living. Also, they're way more expensive than over here so you're probably better off doing an MA here. Can you live at home while you do your MA to save money? If so, take a gap year after undergrad to work full time, and just save up the tuition. During your MA, you can take out a small graduate loan or work a few hours on weekends/in evenings to earn pocket money for going out. The AHRC application was rough but nowhere near as bad as US grad school forms so go ahead and give it a try. You'll need two strong references (another reason to get your profs on board now!) and a detailed research proposal.
Recommenders: your dissertation supervisor will be your first choice as they'll get to know you well over the course of your research. How about seminar tutors? They will know you well. Make a point of speaking up in seminars so they remember you. Try to take at least 2 classes with the same professor in your third year, or take another class with someone who's already taught you so you build up a bit more of a relationship with them and they'll have more to say in a recommendation.
The GRE is a pain. I bought a book way in advance to familiarise myself with the kinds of questions. I devoted a month to studying, doing 1-2 hours per night, 5 nights a week. I didn't do as well as I'd hoped but I think a month tends to be the average. Maybe give yourself 6-7 weeks?
Hope this helps! Let me know if you have any other questions.