There are only two aspects in junior high school mathematics competition: algebra and geometry.

And many junior high school math competitions can be solved by high school math methods.

I taught myself math induction and calculus in grade three. I can handle the algebra part of the competition, but I can't stick to geometry. What I need is spatial thinking, the ability to recite theorems and so on. Specific topics can be found in Baidu: National Junior Middle School Mathematics League and Xinzhi Cup Mathematics Competition.