My recommendations, in order of value, would be:
1) ALL official material (GMAC OG, Verbal OG, GMATPreps, all online questions, etc.)
2) MGMAT - for SC and Number Properties, Word Translations, and additional Quant books as needed. Use their 6 CATs you get free with your books in addition to the 4 GMATPrep CATs from mba.com.
3) For CR, you should get Powerscore's CR book if you need additional help.
4) For RC, I actually like Veritas Prep's RC book to supplement the OG15, but RC is really all about strategy and HOW you read the passages, note-take on them, and use your scratch pad to rephrase the question stems, predict the correct answer, and use process of elimination on the answer choices. There's isn't a fabulous RC book that really delves into the kind of strategy you need, in my opinion.
I would avoid Princeton Review and Kaplan. Really hit all the official material first, multiple times.
Best,
Vivian
