[em10fan]

Get a copy of the Open University (UK distance learning uni, been around since the 70s) books on EBay.

A full set of books for MU123 (The most basic maths course, basically school [age 16] level books) can be had for under £50 on Ebay. Work through them, then move on to the MST124 books which are college [age 18] level), and are also widely available on EBay. Those begin to cover cover calculus, vectors, etc...

I'm 1/3 of the way through doing a maths degree with them, having scraped a C at school almost 20 years ago.