Score Improvement Suggestions

So I took the SAT in June for the first time and got a 1710, (Best in math, worst in writing). I took it again on October 3rd and I got a 1900 (Best in math, worst in CR) I’m planning to retake the SAT in December and I’m shooting for a 2100. Are there any suggestions/resources that could help me boost my score, ideally I’d like to get 750+ in math and not worry about the rest too, too much. I’m generally a good math student and I know the content and to be completely honest it felt as though I got almost every question on the math right, though that’s obviously not what happened. So far I’ve used the blue book (5/10 practice tests used so far) and Gruber’s complete SAT guide. Anything is appreciated!