Is it possible that the test you scored a 680 in(August 28th) and 700(July 21st) may have had a
few repeat questions leading to the inflated score?
In order to clearly understand where you need help, you might have to order
an ESR which might help understand which of the sections caused this score drop
and maybe, once you have an ESR, the experts here might be in a better position
to help you with your should plan your GMAT Preparation.
From whatever preparatory material I have used, here are a few recommendations :
1. Sentence Correction - eGMAT Online Subscription(around 69$) and the Aristotle SC Grail
2. Quantitative Preparation -
GMATClub Tests(These tests give you a clear picture and solving
these questions could help you increase your low 40's to 47-48 and possibly 49/50
3. Without fail, do 4 RC passages everyday and analyze what are the mistakes you are making.
With these things you are much closer to scoring near your goal score(These passages could
be from the Official Guides or any other official material)
4. Also purchase the Exam Pack 2 and the Question Pack1(if not purchased already) and make
sure to refrain from doing any official questions apart from the tests and the OG!
P.S Don't leave any section for too long. Keep in touch with all types of questions(everyday, if possible)
Hope that helps you!