You have a poor foundation, so you'd better buy a reference book with relatively easy exercises and simple knowledge points, such as after-school exercises in textbooks. It's not too late to buy something a little more difficult and comprehensive when you have laid a solid foundation. But I suggest:

Start with the basics. If you are good at math in junior high school, pick up the math textbook for senior one and start from the first chapter. Ask your classmates and teachers if you don't understand anything. You should do every exercise and make it clear.

It should be pointed out that:

First: when you encounter a problem, you must think it over first until you can't do it, and then ask others. Don't ask at first sight.

Second, don't buy comprehensive review materials at first, don't do comprehensive questions and real college entrance examination questions, and it's best to do after-school exercises and basic knowledge points separately.

Third, after reading (listening) and understanding the answer to the question, don't end. Generally speaking, the answer to the question should be handled like this: the first time: see if he did it, the second time, see how he handled each step, and the third time, think about why he did it this way but not that way, and why he used this formula instead of that one. The fourth step is to do another problem, or ask yourself, will you do it again when you encounter this problem? Step 5: Is this the only way to solve this problem? Is this the only way to solve this problem?

Fourth; Slowly, your level will be higher, and then do a comprehensive problem, which must be the topic of integrating the previous knowledge points.

You have a good understanding of the above words. If you practice it, you will have extraordinary gains.