Do you use the OG material alongside the Manhattan math series? For me, question practice was essential for reinforcing the concepts just learned. If you wait until you finish all the guidebooks, then a good bit of the concepts will be forgotten. I made this mistake, and it cost me a lot of time and energy. So remember: Manhattan math and OG at the same time!
I struggled in math for a long time. So if you're in the same situation, look into Jeff Sackmann's math sets
- particularly the fundamental level.
For SC, multiple readings of the Manhattan SC guidebook is important. And make sure to be very aggressive with the OG for SC. That means completing all the questions under test conditions and fully reading every explanation - even for the ones that you answer correctly. And try to be active on the verbal forums. Answer questions and fully explain your reason (why A and not B, C, D, or E).
I was always strong in CR, so perhaps my advice isn't too great here. But the Powerscore CR
Bible and the OG should be enough. Again, be active in the forums.
And as an additional exercise, look into GMAT Fiction
. It won't perform miracles, but you should see some improvement overall after a few books.