Hello,
Well I am also planning to take GMAT by the end of September and according to me
1. Start with Princeton and solve all the sample questionnaire for Quanti'
2. Get on with Kaplan premier and Kaplan gmat 800 and finish the Quanti section
3. Repeat steps 1 and 2 for Verbal
4. Take the preparation test from princeton, kaplan and GPrep
5. By watching the results you should be able to figure out where you lag and brush up again on those topics
6. Books I am using includes Kaplan 800, kaplan premier edition, kaplan verbal workout, OG and Princeton
These books should be more than sufficient for you to get proper "fundas" for quantitative and verbal.
All the best,
Cheers,
Sammy