Hi joannaecohen,
From your post, it sounds like you're thinking about 'brute forcing' your studies by doing lots of practice questions (as a means of trying to gain expertise). Unfortunately, that type of approach would likely take far longer than you want it to (assuming that it would work at all). The OG books are great sources for practice questions, but they're not designed to teach you Tactics, patterns or the little 'secrets' behind the GMAT - for those, you'll need Course-oriented materials. In that way, 'quality' of study is more valuable than 'quantity' of study (although you'll likely still have to do plenty of study to achieve your goals).
1) How long have you studied?
2) What materials have you used so far?
3) How have you scored on each of your CATs (including the Quant and Verbal Scaled Scores)?
4) What is your goal score?
5) When are you planning to take the GMAT?
GMAT assassins aren't born, they're made,
Rich