The provincial team is a rare thing, and the sense of luck in the math competition is very important. Unless you are a very high-level player, I suggest that you set the goal as the first prize in the province (even a player will make mistakes and won't make it to the provincial team). Therefore, you must learn other subjects well first, so that when you go to the competition, you will feel that you have a future and there will be no too much pressure.

Before joining the provincial team, I suggest that you don't do too many difficult problems (such as CMO and IMO), which will not only waste time, but also affect your thinking of solving league problems. These things can be learned in time after entering the provincial team.

You don't need much preparation for the preliminary round, because the difficulty of the preliminary round is similar to that of the rematch (different provinces, but it won't exceed the scope of the rematch), so just prepare for the rematch. If you are only a freshman now, finish your high school knowledge first, and then do more college entrance examination papers (this was taught to me by someone from our provincial team the year before last, and finally he won the first prize of CMO). It is no problem to do more college entrance examination papers. As for competition knowledge, I suggest you make a competition outline and then buy a competition book (the kind that talks about special topics). If your school has training and can talk about general topics, you don't have to read books by yourself. There are many such books, please ask your teacher to recommend them to you (I used pre-competition training, which is quite good). Of course, you have to do the exam questions of previous years. After you finish, you should pay attention to analyze what the league exam is. Personally, I don't recommend studying middle school mathematics. I feel that it is better to learn knowledge systematically. After all, you have less time and can't finish reading so much middle school math. Then classes are usually suspended before the exam. At this time, we should do more simulation questions. If you find a weak topic, take out the book and reread it. At other times, we just read the books and papers we have read before, do the wrong questions again, and then try our luck in the final exam.

In your case, I don't think there are many opportunities to join the provincial team, but I might as well give it a try. It would be great if you can get the first prize in the province. You can add 20 points to the college entrance examination (which can be added in most provinces), and learning these is also very helpful for the college entrance examination and self-enrollment mathematics.