I skimmed all the replies below - this is years of learning and study - so I ask: Is there some dependency order someone could quickly sketch out for some of these topics? Eg, linear algebra comes before X? HN is an incredibly useful crowdsourcing resource for the self-motivated!
The minimal classical way to bootstrap your math knowledge is algebra (mostly linear) + analysis. This is the approach used by e.g. Harvard Math 55, which is a really famous course. Harvard Math 55 employed Halmos + baby Rudin as main textbooks. Halmos has now been replaced by Axler, which is an excellent textbook (but the typographic changes in the last edition are very distracting). Rudin is probably too synthetic…
I would love a bootcamp like that. Or even one that helped you with proofs. I've found that's my biggest issue trying to teach myself pure mathematics. I just can't start the damn proof. Once I get the start, I can usually finish it, but starting the proof I just feel so clueless how to do it.