The standard advice is to get the assigned books (or highly recommended books) for each of the courses in your coming semester and work through them early. You

The standard advice is to get the assigned books (or highly recommended books) for each of the courses in your coming semester and work through them early. You can support them with other resources but you’ll save yourself a lot of time by using them as your main guide - especially for higher level math. The hard choice is how to study from the books. The only general tip I can give you is to not get too caught up in the early chapters. It’s better to do a fast first pass then come back to it later.