I take a different perspective on GMAT, and at that, I think a better approach (personally speaking).
A 700 GMAT is a great score as most would agree with me (and if not, the 90 percentile speaks for itself). I don't like to view the "Indians are over-populated in the applicant pool" perspective, but instead, I look at the GMAT as GMAT itself. How have you done on your practice tests? Were you consistently getting 740 or more on GMAT? A onesey or twosey of 720 isn't really a good indicator that you'll perform 720+ on a real GMAT. However, a string of 6 CATs that indicate you have an ability of 750 might mean to you that you should re-take the GMAT. If you're scoring around 700 (+/- 20 points), you're in range. And with that said, a 720 won't really help you any more than your 700. At this point, the return on the GMAT score has greatly diminished because it's extremely hard to improve a 700 to a 740 (unlike a 460 to a 500). If you don't think you can score 730 or higher, I wouldn't worry much about the GMAT anymore, but instead, I'd focus more on the applications. There's no point in comparing GMAT to the greater Indian pool because I believe GMAT is one great hurdle that only you yourself would know what your capable of. It's not efficient anymore to try to achieve the average of something when the correlation between the average and your score is big. Instead, utilize the time you would've spent studying for the next GMAT exam on school preparation and essay-crafting.
Building an alternative transcript is a smart thing to do, especially for an applicant whose undergrad grades weren't as high as they'd want it to be. In terms of what courses to take, opt for quantitative-oriented courses, such as calculus, statistics, accounting, and economics. The courses themselves matter less than the grade that you acquire from taking the classes. Get A's to prove that you can do it. Your quant will probably not be a big issue, as you mentioned of your Q50 on GMAT. Look at your undergrad transcript and look at how you've performed in quant-oriented courses. Did you get mostly A's or Bs in them? If you had more A's than B's in math courses, chances are your math is fine and you don't have to worry about it. But all things aside, building an alternative transcript is a great way to show dedication and intelligence to AdComs who may have a few doubt in someone's undergrad transcript.