Hi Anila,
Many Test Takers are unhappy about their initial Diagnostic CAT scores, so you're not alone. While this score is low, it's worth noting that you don't really know that much about the GMAT just yet, so you will naturally improve as you learn more about the content and practice the proper Tactics. That having been said, raising this score to a respectable level (so that you can apply to the Schools that you listed in your profile) will take some serious work - and you'll have to make some BIG improvements to how you handle BOTH the Quant and Verbal sections.
Before I can offer you the specific advice that you’re looking for, it would help if you could provide a bit more information on your studies and goals:
1) Did you run out of time on this CAT and leave any questions unanswered?
2) Did you take the FULL CAT (with the Essay and IR sections)?
3) What is your goal score?
4) When are you planning to take the GMAT?
5) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich