My GMAT Practice Scores: 510 - 650

I had similar scores when I started to prepare for GMAT.

GMATPrep : 560, 580, retake : 550 , 620.
Kaplan : 530, 520
Princeton: 520, 570

I would suggest the same as what I did: (It may not be the best solution but it has helped me a lot)

1. Instead of rushing and taking more and more tests. Try to go slowly building solid foundation.
2. Start with Manhattan SC and maintain error log. (Do SC for at least 4-5 days) Solve as many problems as you can.
After 5 days review your mistakes from error log and mark the repeated one's with RED (weakness).
3. Powerscore CR bible : try to read each and every details. Solve as many problems as you can after that for 4-5 days.
4. Do the same for Maths: Instead of rushing to difficult questions try to solve simple questions to build foundation.
5. For RC : I need to work on it . So no suggestions. Practice is the key.

After this try to take one test to check your progress.

I repeat: don't just rush to take test.

Thanks - that is helpful. I admit that I am guilty of trying to rush things. I will have to spend some more time developing my fundentals.

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GMAT Prep is the most reliable indicator but even GMAT Prep has a 40 point variance on a day-to-day basis. (Meaning if you took 2 in a row, you could have scored as much as 40 points apart, and that's "normal").

You can take a look at the gmat score estimator/calculator to help understand scoring across the board.