Ask HN: How can I learn and get better at maths on my own?

I’d call what you want to do “teach yourself maths as a foreign language”. It can very much be done because I did it.

If I could do it all again, I’d start with an old school Calculus course. E.g “Calculus” by Binmore . It’s a decent and well explained introduction to Calculus and Linear Algebra and it’s useful maths. You have to get a hang of thinking in maths and doing maths you find boring.

From here it depends on what you want to do. There’s more maths out there than there is time so you need goals.

Go to expii.com and start doing a module to test where you're at. You do exercises and if you don't get something, it shows you a 5min lesson. It's a startup by the guy who coaches the US olympiad team. When you're done find some introductory text that goes about proving things, such as Hoffman & Kunze Linear Algebra or Concrete Math by Knuth et all. Concrete Math is accessible to a motivated highschool student. You have Math stackexchange to ask questions or hire a tutor from a local university to walk you through some of the proofs at a coffee shop on a Sunday afternoon. I paid a grad student to review my terrible attempts at proofs when I started going through the exercises of these intro books, highly recommend you do this too.