While I am still not a quant expert I loved the

Kaplan GMAT/GRE math workbook (went through it twice and am going to go through my trouble questions for a third time). It isn't huge on concepts, but if you go through all 388 questions you will have a good base to start from.

Kaplan 800 picks up where the math workbook leaves off as it touches some subjects that were neglected in the workbook. From there I would focus on some of the advanced topics like combinations, high level statistic questions, number theory, high level algebra, probability........

Right now I am making my way through the official guide workbooks which are supposed to be slightly more advanced than the

OG 11. I think the OG is a huge must for verbal.

Kaplan really doesn't do a great job with the verbal section. But I believe the

Kaplan math materials are great!