Hi Sanath,
There are certain subjects in the GMAT that require more 'technical' knowledge than others. For example, Geometry questions often require that you have knowledge of specific math formulas to get the correct answer. Sentence Corrections have that similar requirement (but instead of math formulas, you need to know grammar/idiom rules). To consistently hit 700+, you're going to need to have all of that necessary knowledge AND you'll need to do organized work on your pad AND you'll need to avoid making silly/little mistakes. Training to score at that level takes a certain amount of time and effort - and approximately 90% of Test Takers either CAN'T or WON'T do what it takes to EARN that Score.
With an early October Test Date, you have plenty of time to study and improve, but you'll have to be really efficient with your studies going forward. Beyond doing lots of practice problems though, you need consistent, professional guidance, so that you can learn all of the patterns, tactics and 'secrets' of the GMAT (without having to try to figure out all of that stuff on your own). You would likely find it beneficial to invest in a GMAT Course of some kind (either Guided Self-Study or instructor-led). Most GMAT Companies offer some type of free materials (practice problems, Trial Accounts, videos, etc.) that you can use to 'test out' a product before you buy it. We have a variety of those resources at our site (
www.empowergmat.com). I suggest that you take advantage of all of them then choose the one that best matches your personality, timeline and budget.
If you have any additional question, then you can feel free to contact me directly.
GMAT assassins aren't born, they're made,
Rich