Help getting good at math.

My background: I took algebra 2, trig, geometry and precalculus in high school and coasted through with b’s and got a 680 on the math sat with minimal effort. My issue is that while I may be able to solve those specific problem types I don’t have much of a mathematical intuition and don’t feel like I actually understand math too well. I also have some experience teaching myself other stuff.

My plan: I’m taking calculus in uni this year and in addition I want to teach myself statistics and discrete math. I plan to read through some textbooks, solve the exercises and watch lectures on YouTube.

My questions:

1. Any tips for building a stronger intuition besides just grinding problems
2. Any areas of math I should look into in particular or avoid.
3. Where to find banks of practice problems besides textbooks
4. For the subjects I’m teaching myself how should I test to know when to move on
5. Any book recommendations (for the specific subjects I’m learning, general math or for math intuition) (textbook or non textbook either are fine)
6. Any general tips or tricks