Sorry for the late reply. Midterm week was pretty hellish. I'm not sure what areas to research yet. I like anything visual, like geometry. i thought about topology, but have heard the concepts are very challenging to grasp. I also really enjoyed a discrete math course that I took last semester, so possibly number theory, combinatorics, or probability.
As far as coursework I have only had a couple of semesters of calculus and a graduate course in discrete math. I'm guessing that I would still need to take multivariable calculus, linear algebra, and maybe differential equations (not to mention the GRE subject test) before applying to PhD programs.