Went from a 1370 to a 1560 on college board practice tests in just two weeks.
The thing that helped me the most when it came to getting an 800 in reading was definitely the SAT reading explained video. I didn't have much knowledge on punctuation before watching and rewatching the video so the explanations were really useful.
The GPT prompt also helped me a ton and was my main source of practice. The only real problem with it is that--especially on the math section--it often generates questions with no correct answer in the answer choices.