LogFAQs > #980221339

At this point you might want to dip your toes into some higher level math stuff like Real/Complex Analysis, Topology, and Abstract Algebra.

Will you remember every proof or will any of the stuff in those classes be everyday useful like stats? No. But they are pretty much foundational courses for higher math and once you go through them it makes learning more advanced applied math topics (partial differential equations, stochastic processes, fourier analysis, mathematical statistics, etc.) much easier to get through.

Edit: To put it another way, you were getting frustrated by the fact that trying to learn more math on wiki keeps sending down endless rabbit holes. Basically those rabbit holes will mostly all lead to the subjects I mentioned. Its why they are all required for math phd programs.