[henearkr]

My own way to expand my knowledge was by going through textbooks and with a heavy support of Math StackExchange.

Maths is a very written-oriented domain, but still if you are more a video-oriented learner you can probably find a lot on Youtube, and a lot of great researchers have videos there.

[cmehdy]

To add to this, "All the Math books you'll ever need"[0] compiles a fantastic list of books for all aspects of mathematics.

[0] https://mathblog.com/mathematics-books/

[henearkr]

Good one for a starting point!

However the books I read are not in it lol...