Calculus: Thomas, Weir & Hass - Thomas' Calculus

Linear Algebra (which is what you really need): Gilbert Strang - Linear Algebra and its applications

These two are all you need, with which you'll get a solid base. Then you're good to go on your own. These two combined are about 4 semesters worth of work. But if you really focus, I think you can get them done in a little less than 6 months.

If you want a 'just what I need' approach, Khan Academy.

For self-study, you don't necessarily need to follow the usual progression of math classes that start at calculus. It's more important to get comfortable with linear algebra than calculus, especially the way a lot of intro calculus courses focus on calculating integrals and derivatives. Maybe it's not the best message, but the worst grades in my math degree were in the intro calculus classes.

I don't remember what intro linear algebra books I used, but my college uses this: https://www.math.ucdavis.edu/~linear/ (I took the class before this free textbook was developed).

Spivak calculus. There is nothing like it. You will learn how to think in math, not just calculus.

Whoa! I was just talking about this text book the other day! I think it's out of print these days, but it's a hidden gem!

This Reddit post by a struggling Phd student has some great advice on catching up on maths.

https://np.reddit.com/r/MachineLearning/comments/73n9pm/d_co...