Focus as much as possible on the underlying concepts from any math topic and how they connect to other concepts. Try to boil these concepts down to the most simple, clear form that makes sense to you. Test your boiled down conceptual understanding by applying it to related exercises/problems you haven't tried before and seeing what happens.

For each sub-topic, most math books give you the tools first and then teach you problems they should be used on. Read the problems first, and think how you might solve them (don't expect to figure it out, but if you do, great!). Then, go back and learn the tools, trying mostly discern the "how" and the "why" as opposed to the "what". Math is all about "how" and the "why". As some motivation, whenever a new thing clicks, it is very satisfying! :) But it definitely is a tough process.

Good luck!

Textbooks and exercises. Avoid shortcuts such as online tutorials or anything with "for hackers" in the title.