Hi Aseem,
The PhD application process tends to be a bit more 'rigorous' than the MBA application process is - since there tends to be a small group of highly qualified applicants competing for a relatively small number of PhD 'slots.' As such, beyond having a strong GMAT Score, you'll need a strong OVERALL profile and you'll need to properly 'market yourself' to each individual Program that you apply to. By extension, you would likely find it beneficial to speak with an Admissions Expert about your overall profile and plans. There's a Forum full of those Experts here:
https://gmatclub.com/forum/ask-admissio ... tants-124/Since it sounds like you're just beginning your studies, then it would be a good idea to take a FULL-LENGTH practice CAT Test; you can access 2 for free at
www.mba.com (and they come with some additional practice materials). If you want to do a little studying first, so that you can familiarize yourself with the basic content and question types, then that's okay - but you shouldn't wait too long to take that initial CAT. That score will give us a good sense of your natural strengths and weaknesses and will help provide a basis for comparison as you continue to study. A FULL CAT takes about 3.5 hours to complete, so make sure that you've set aside enough time to take it in one sitting. Once you have that Score, you should report back here and we can come up with a study plan.
As an aside, the 750+ score is approximately the 98th percentile - meaning that most GMATers never score that high on the Official Exam. Thankfully, NO Program actually requires that you score that high - so it's important to realize that the score that you "want" and the score that you "need" to get into your first-choice Program are likely not the same thing.
I'd like to know a bit more about your timeline and goals:
1) Going forward, how many hours do you think you can consistently study each week?
2) When are you planning to apply to School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich