Hi akshitagandhi,
To answer your immediate question: you do not need the online study materials that come with
the Official Guide to earn a high Score on the Official GMAT. There are a variety of different study materials that you might use during your studies - and your particular 'needs' will depend a great deal on how effectively you can learn the proper Quant and Verbal Tactics to earn a high Score on the GMAT.
From what you describe, your immediate study plan is 'book heavy'; unfortunately, many GMATers who study in that way end up getting 'stuck' at a particular score level. Even the best books are limited in what they can teach you; they also can't force you to approach questions in a certain way and their explanations are often one-sided. There's no harm in starting off your studies in that fashion, but you'll likely end up needing to invest in some additional, non-book resources at some point.
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.
I'd like to know a bit more about your timeline and goals:
1) What is your goal score?
2) When are you planning to take the GMAT?
3) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich