Basically the critical reading is the section that needs a long term strategy to ensure that you get over a 700. It really just comes down to vocab and how well you absorb things when you read. Short term tricks are don't help as much for this. However, the writing and the math section, I almost discourage long term prep, especially if you are scoring above 600. The best time frame imo is the summer.
What worked for me was working with a writing workbook type book, which broke out all the different grammar topics that are tested on the exam and then had a bunch of drills that made sure you totally understood everything forwards and backwards. Afterwards, I went through the blue book and did the practice tests. Just going blind into practice test after practice doesn't help. It just wastes good practice material.
For the math, I also used a workbook that broke out all the topics, just like the grammar.
Doing this, I spent just a couple of hundred dollars on books rather than paying thousands for tutors or prep courses. But I'll caveat this by saying that it wasn't easy because I had to be super dedicated that summer.