Many people are overwhelmed by the sheer breadth and diversity of study material available for the GMAT and GRE. Let me help. The following is the basic checklist for what you should complete (independent of good tutoring, of course) in order to be basically prepared to score respectably on the GMAT:
Quant:
1) MGMAT Foundations of GMAT Math Guide
2) MGMAT All the Quant
3) GMAT Club Paid Subscription– Do practice sets on all Quantitative problem types
4) GMAC Official Guide Practice Problems, from the combined official guide and also the separate Quantitative Review
5) MGMAT Advanced Quant
6) GMAC Advanced Official Guide
Verbal:
1) Powerscore critical reasoning, Sentence Correction, and Reading Comprehension guides
2) GMAC Official Guide practice problems from the combined Official Guide and also the GMAT Verbal Review
3) GMAC Advanced Official Guide
Altogether:
MBA.COM practice tests– I like to stick to the official practice tests
The Manhattan ones are probably second best, but a distant second. The disadvantage of the MBA.COM tests is that they give less detailed analysis and do not provide question explanations, but all of the questions are explained on my Youtube channel or on GMAT club, and the MBA.COM tests are the most accurate
…And for the GRE:
1) MGMAT Quant and Verbal Strategy Guides
2) ETS Official Guide practice problems, including the overall official guide and the separate Quant and verbal guides