Hi Vamsi1410,
Many Business School Programs expect applicants to have 2-3 years (or more) of quality Work Experience when they apply to School. Since you're interested in "top" Programs, you have to anticipate a high level of competition (and a high volume of it), so you might want to think in terms of how strong your OVERALL profile would be without any practical Work Experience, leadership roles, etc. You might also find it useful to research the specific Programs that you're interested in, so that you can better define what you might "need" to apply.
All of that having been said, if it turns out that you won't be applying to Business School for several years - so that you can earn the Work Experience that you'll likely need - you can still take care of the GMAT now (since the Official Score is valid for 5 years) and not have to worry about it later.
GMAT assassins aren't born, they're made,
Rich