There are few threads in BTG that has links for free resources.

I found this useful:
https://readyforgmat.com/math/documents/ ... rsion2.pdf

First step would be to analyze where you are going wrong, whether it is Quant or Verbal. Secondly, I would look at which section within Quant or Verbal. This would give a better idea of which section you want to attack to gain maximum score in your GMAT. Rather than attacking higher end tough problems, you may even realize that the basics maybe OFF. So, you need to really breakdown your scores before you make a decision.

I really have to agree with Mourin. It's not quantity of study that changes your score, but quality. Where are your weaknesses? What question-type is your best or worst? What skill areas need the most work? That's why Grockit's statistics are set up by skill tag -- it's hard to improve without extensive review of percentages correct/incorrect per content-area.

Looks like you know the content, especially if you're in the mid to upper 600's, but I think harder questions are slipping by you because your strategy might not be as solid as you think. I'd focus there.

I have a small doubt in a CR question:

Student enrollment at Central High School has declined in each of the past five years by an average of 7.9 percent, although graduation rates have risen. Therefore, the school should focus less on graduation rates and more on trying to attract new students.

The answer to which of the following questions would most likely point out the illogical nature of the conclusion drawn above?

1)What would be the consequences of an increased student dropout rate?

2)What is the average age of students applying to study at Central High School?

3)Are students applying at other high schools more academically committed?

4)Where are graduation rates of regional high schools compiled?

5)How would the school budget be affected by a new student recruitment program?

hey...
My situation is similar to yours. I am confused about the advanced material to refer next. I have done MGMAT guides, OGs, kaplan 800, powerscore cr. Even if i know the topics i am weak in where do i practice them from?

Advanced material for what ? Quants or Verbal ? Preferably you can go through the Mgmat guides again or try their Advanced Quant book. For Verbal I found Aristotle very useful. They have a lot of questions too.