User blog comment:Mush9/NOOP function/@comment-24920136-20161112215055/@comment-1605058-20161113083822

The most important thing for you to learn is definitely predicate logic, which is really a framework underlying (nearly) every formal theory. The next step would be to learn basics of set theory, preferably first from an informal perspective (to get some grasp of the concepts) and only then on a formal, axiomatic level.

I'd love to recommend some sources on that, but to be fair I don't know any, because my logic and set theory self-education was incredibly unorganized.