<p>First of all, I suggest you ask this on the artofproblemsolving.com, where you’ll probably get many more answers. And yes, AoPS 1 & 2 both help a lot, and the Intro/Intermediate subjects are even better for subjects you’re not familiar with. They’ve helped me improve <em>so</em> much. You should also consider AoPS online classes if you’re willing to spend the time and money. Good luck!</p>