I was in your shoes back then too! Although it took me around a month to get above a 650. You're luckier than me since you got a good verbal score (above 30) on your first try. To improve quant, there were a couple of things I did.
1.
Work on concepts through MGMAT books. I'm not sure whether you have studied the series but even if you did, chances are you might just be breezing through them instead of understanding how to approach the question systematically. Your goal is to be able to produce these systematic approaches during the exam.
2.
Do GMATPrep CATS. GMATPrep CATs are by far the best at simulating the exam experience. I suggest you but the bundle available on GMAC website that sells one question bank along with the two exams. It has discounts too I think and it's super worth it.
3.
Create an error log. What I mean by an
error log is a way to find out which areas you are weak at. Around week 3 of studying you should be able to gather enough information to spend on the last week fixing your silly mistakes.
4.
Learn from others. Through the questions you do, try to find online solutions where peeps at the GMAT club have come up with their own way of tackling problems that may be faster than what you are doing. As you participate with the forum, the more active learning you engage in. This will allow you to feel less panicky in the exam room have versatile approaches along with systematic approaches to your quants.
5.
Practice on the official guide! The first 200 questions are easy and you should aim at getting 95% above accuracy rate. After those 200 questions, you will encounter much harder math and you should aim to understand what's the best way for you to 1) mitigate mistakes 2) solve questions quickly.
I suggest studying at least 3 hours per day on the questions. Good luck! Shoot me a PM if you have any questions