[gtani]

Look at UIUC and Open University, MIT's OCW, community/junior colleges can give you a big boost, there's probably a lot of other advice at /r/math, /r/LearnMath and math.stackexchange.

Some older threads:

https://news.ycombinator.com/item?id=19811715

https://news.ycombinator.com/item?id=18939913

https://news.ycombinator.com/item?id=19071050