What were your scaled scores for GMATPrep? Knowing your scaled scores could tell you where you could improve the most, verbal or quant.
I'm in the same boat as you. My college GPA is terrible and am aiming for a 710+.
I would study your books first and use CATs periodically to assess your progress after each book/chapter/topic. Also, for me, I felt that using CATs before studying was a waste because there are things I've simply forgotten and would have no way of answering several math questions without guessing (for example, questions over geometry formulas)
If you can get 22 CATs, then use them all, but buying 22 CATs kinda sounds like a waste of $$ to me. For me, its good enough practice going over questions I got wrong, why I got them wrong, and how to solve them efficiently. CATs are more for assessing your progress and practicing with time restraints. But without studying the information first, CATs are almost pointless.
GMAT Retake - Summer/Fall 2010 Minimum 650, Goal 700
Resources - Kaplan Premiere, MGMAT Guides 1-8, OG12, Quant & Verbal
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