Mathematics and science (I don't know if you are a liberal arts or a science? It is also a waste not to buy anything else. If the unit evaluation is better, it will be finer, deeper and more difficult.
Only in this way can we grasp it more firmly.
In addition, you said that your foundation is poor, so I suggest you try to optimize the design training (basic version, Ren Zhihong's), which is very suitable for a round of review exercises, closely related to textbooks, and very suitable for grasping the foundation.
I won't say much about the rest. In the days before the college entrance examination 100, the space for improving mathematics is the biggest one. Besides reading books, doing test papers is absolutely effective. Don't listen to other people's nonsense It's no use doing the problem. Everyone knows that the sea of people tactics is a very useful method, which will improve you by at least 20 points!
I wish you a smooth college entrance examination!