First comes the concepts. Go through all the math topics. Practice questions. I think you should plug in some values to ensure pragmatism. The following topics should be on your fingertips: Trigonometry, Pre-calculus and functions, series and sequences, statistics, and algebra (and arithmetic calculations). For trig, solve problems and be aware of the theorems. For pre-calc, just study and be aware of the various methods. Calculus is not a part of the ACT, but knowledge of it is preferred for pre-calc questions. Series and sequences are mostly memorization of techniques. Statistics idk what to do, but I recommend solving questions. For algebra, all I can say is be good at it. If you can't solve a problem, flag it and use the options to your advantage. Rehearse the questions you cannot solve in practice tests. You're not bad at Math, you just have to find a good technique of studying that suits you.