Hi rajatredhu,
Based on what you've written, there are a number of different 'issues' to consider (and many of them are details that YOU have to define):
1) It's not clear when you want to apply to Business School and it's not clear if you have any specific Schools/Programs in mind. Defining these details will help to define the timeframe that you have to work in and the specific tasks that you will need to complete.
2) If you haven't started studying yet, a 750+ score goal might be a challenge. Many Test Takers spend 3 months (or more) to hit their 'peak' scores, so you have to consider the amount of time that you'll need to commit to studying.
3) Quitting your job is probably NOT a great idea, but you can decide how long you can go without having an income.
Considering that we're nearing the end of September, and you would have to get so much done to make the upcoming Round 2 deadlines, it might be in your best interest to plan to apply to Business School NEXT year (in Round 1 or Round 2). In this way, you would have plenty of time to study for the GMAT, research Schools, plan your applications, etc. and put together the strongest application possible.
1) Have you done any studying for the GMAT yet?
GMAT assassins aren't born, they're made,
Rich