Looks like verbal has been your achilles heel... you've scored 44-48 in quants in all 3 attempts - if you maintain that and improve verbals, you should do much better.
Also, your second GMAT score of 640 looks a pretty decent score, with a good balance between quant and verbal - are you sure you want to retake despite scoring 640? f you want to target 700, you have to maintain quants at 48-49 and ramp up your verbal score to 36-37. That means serious efforts on both - especially verbal.
I suggest you give yourself a good 2-3 months to work real hard with renewed vigor - and sit for GMAT again only when you find your practice scores improving to these levels. It's no use just sitting for another GMAT, hoping for the best, otherwise.
Have you looked at e-GMAT
? The feedback from users has been very good and it is targeted at non-native speakers. Try their free material first and take the paid service if you like the free stuff - could help give a structure to your verbal prep.
Have you gone through the SC, CR and RC 600 and 700 level question threads on GMATClub? They contain a wealth of questions and interesting and helpful discussions on how to solve them.
Pls go through the SC guides available on GMATClub, by whiplash, Gayathri and Spidey - I have found them invaluable.
Last but not the least, go to whiplash's profile, download all her verbal guides and documents available in her signature - they are gems.
All the best!
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