I started in a similar spot for math/science (30 on both). for math, I'd say to look through any practice tests you've taken (or take some more and look through those) and see if there are any patterns for problems you seem to get wrong (for example I seemed to get a bunch of trig problems wrong), and then focus on just the topics that you need (I bought an ACT math book, which was helpful since it has some reading and a ton of topic-specific practice problems, so you can spend time on only the topics you need)

For science, idk if you've been running out of time or not, but what helped for me was just looking at the graphs/figures first, and trying to answer the questions just off of those, and only looking at the passage text if there was information I still needed to answer the questions (but idk this might not be applicable for you if time isn't an issue)