I went from 0 to Quantum Mechanics, here's how:
1. Get a reference book which is easy to flip through and has all the main things like fractions, decimals, scientific notation, logarithms, etc. This will save you a ton of time. I suppose wikipedia will do these days.
2. Go straight into algebra 101.
3. Go take trig 101
4. Take Calc 101, 201, 301
5. Take Differential Equations and Linear Algebra
6. Take 2 years of Math Methods in the Physical Science
7. Take Quantum Mechanics
I know it sounds simple but it takes a lot of time. The idiot guides are helpful for reviewing thoroughly.