Hi ashokjha1986,
You should study for around three months to achieve a good score. Its a good thing you have taken a practice test. You can now know your weaknesses and work on them. If you are willing to study dedicatedly for that period, you are sure to achieve your goal. I believe you may benefit from taking a GMATPREP course.
Your choice of using
MGMAT guides for your preparation is great.
MGMAT guides are phenomenal and cover the entire syllabus really well. I must add that if you are particularly looking to discover and improve on your weak areas in quant; a subscription to
GMATCLUB tests is the best way to do that. They are indeed phenomenal and will not only pinpoint your weak areas but also help you improve on them.
Also for verbal, I would highly encourage you to consider
e-gmat verbal online or the
e-gmat verbal live course. They are both amazing courses especially designed for non-natives. They offer almost 25% of their courses for free so you can try out their free trial to decide which one you want to go for. Plus the
e-gmat Scholaranium which is included in both the courses is one of the best verbal practice tools in the market.
Further taking multiple mocks might help. Apart from the GMATPREP,
Manhattan GMAT tests and Veritas Prep Tests in my experience have a good verbal and Quant section and will certainly help you point out and improve your weak areas.
Further another advantage of taking many mocks is to build up your stamina. Apart from the GMATPREP tests, taking practise tests of any major GMATPREP company ought to do that.
I would also encourage you to purchase the latest version of
OG and the verbal review for some great additional practice. Here is a link that will help you with your decision.
https://gmatclub.com/forum/best-gmat-ve ... 68383.htmlLastly, you can check out a very interesting article by Mike McGarry from
Magoosh detailing a 3 month study plan
https://magoosh.com/gmat/2012/3-month-g ... -students/. You will find it very helpful as it gives out a study plan as per your needs.
Hope this helps. All the best.