Hi shantanu.agarwal,
While I can certainly sympathize with people who are on a limited budget, trying to prep for the GMAT by not spending much money is, for most people, a huge mistake. If you're not properly prepared to take the GMAT, then you'll end up taking it more than once (at $250 per test). In addition, Business School is a remarkably expensive investment. If you're aiming at Top Schools, and possibly scholarships (which will save you LOTS of money later), then you'll need a top GMAT score just to compete. This is all a round-about way of saying that you should think about investing a bit of money into this process.
GMAT assassins aren't born, they're made,
Rich