Hi OK735,
Statistically-speaking, raising a 500 to the point that you can consistently score 650+ will likely require at least another 3 months of consistent, guided study - and you would have to make significant improvements to how you handle BOTH the Quant and Verbal sections. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level. Of course, that type of score improvement might take more or less time, depending on your skills, strengths and weaknesses when it comes to this Exam.
To properly assess your situation, it would help if you could provide a bit more information on how you've been studying and your goals:
1) What were your Quant and Verbal Scaled Scores for this 500?
2) How long have you studied? How many hours do you typically study each week?
3) What study materials have you used so far?
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