Should I schedule more tests?

For context, I am a nontraditional college student who never took the SAT or went to public school. I scheduled a test for September just so I CAN apply to a couple schools currently requiring test scores for transfer students. My score matters but not really. I want to get a 1500+ because most of the schools that require it are top, competitive schools, but it's not the end of the world if I get 1400+.

I recently rushed a practice test after finishing the beginner unit on Khan Academy and got a 1200, 600 in each test. All the R&W questions I got wrong were 100% because I didn't understand the question or the word definitions, and I had to skip half of the math section because I didn't even know how to solve them. I'm entering Calculus II but I skipped a ton of math because of how the GED-College pipeline is.

I think I could easily improve to a 1400 if I just finish the Khan Academy units, but should I schedule two test dates? I don't do super well on tests but I'm pretty confident I could at least get a 1400. I'm mainly just worried because some of this content is kind of fresh for me, and there isn't a lot of locations available in my state, so spots fill up fast. I can afford scheduling multiple.

I'd also appreciate any study tips. Should I skip the middle section on Khan Academy and focus on practice tests, or should I focus more on studying and using the tests as a metric?