Hi kumarpushyamitra,
It sounds like you are just beginning your studies, so it's important to define your situation (plans, goals, etc.) and pick the GMAT resources that will best match your goals.
1) What is your score goal?
2) When are you planning to apply to Business School?
Many Test Takers spend 3 months (or more) on their studies; during that time, it's common to spend 10-15 hours (or more) per week studying for the GMAT, so this is a BIG task. Thankfully, the GMAT is a predictable Exam, so you can learn everything that you need to know to score at a high level. I can recommend the GMAC Official Guide (the 13th edition or the 2015 edition - they're the same book) and the free material that you can download from
www.mba.com.
Early on, you should plan to take a FULL-length practice CAT Test to establish your "baseline score" and get a sense of your strengths and weaknesses. 2 free CATs come with the material from mba.com - a full CAT takes about 4 hours to complete, so make sure that you've set aside enough time to do so. Once you have those scores, you should report back.
If you have any additional questions, then you can feel free to contact me directly.
GMAT assassins aren't born, they're made,
Rich