Most colleges accept a superscore, meaning that you can submit your highest score on each individual section even if those scores come from different tests. Take both the ACT and SAT, see which one you have a higher percentile on, then study for it more and take it again. This will allow you to superscore on whichever test you are better at taking.
Here is a list of things to bring: a snack, a calculator, extra batteries for the calculator, a mechanical #2 pencil, a regular wooden pencil, a water bottle, a mask, a jacket, glasses (if applicable), and a good eraser.
Khan Academy can be connected to your CollegeBoard account (here is how) to show you which areas you did well on as well as which areas need work. It will give you practice questions and tests based on what you need as an individual.
Good luck from Simple Studies!