If you want to cross 700-750 threshold...

You need to go back to your previous mistakes and analyze where you are making the most mistakes. Your analysis needs to be a deep dive of what kind of questions you attempted incorrectly. For math strategies - I recommend Manhattan GMAT (they do online classes - absolutely awesome ones like real classrooms); they also have pretty good sentence corrections. For verbal - Refer to Critical Reasoning Bibles. Go through every single page twice! These have way too many details and you'll miss something if you're just reading it like a book. For Practice tests that are challenging - refer to Kaplan GMAT 800.

This will help break down all the different kinds of strategies and sub strategies that GMAT asks in the test. Once your basics are crystal clear only then you can score high. For 700-750 you need to be accurate, there is no margin for error and guesswork. You need to know GMAT inside out. That requires an analytic mind.

It's not about number of practice tests, its about building endurance to sit through the exam, its about re-taking enough times and going through uncomfortable long test taking painful sessions so that GMAT day is a smooth day - a beautiful day. People only see the "Results" ...what goes into getting that score...its another story. I speak from personal experience.

It's about self-discipline.

Good Luck and wish you the very best. Keep up your spirits, don't get disheartened and continue working towards your ultimate dream!