Hi Vvin,
To start, if you are not scoring close to your Score Goal yet, then you should not 'rush in' to take the GMAT (you will likely just end up paying to retake it again later - so you can save some time, money and stress by pushing back your Test Date so that you can put in the additional study time that's needed).
As an aside, the 750+ score is approximately the 98th percentile - meaning that most GMATers never score that high on the Official Exam. Thankfully, NO Business School actually requires that you score that high - so it's important to realize that the score that you "want" and the score that you "need" to get into your first-choice School are not the same thing.
Before I can offer you the specific advice that you’re looking for, it would help if you could provide a bit more information on how you've been studying and your goals:
1) How many hours do you typically study each week?
2) On what dates did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
3) Are you planning to take the At-home GMAT or are you planning to take your GMAT at a Test Facility?
4) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich