Hi adityadon,
With a Test Date at the end of May, you've given yourself plenty of time to study, which is good. Most Test Takers spend 3 months (or more) on their studies; during that time, it's common to spend 10-15 hours per week (or more) on the process.
The 610 is a solid "baseline score"; did the Test include the Essay and IR sections?
There are a variety of resources that you can use during your studies. Most GMAT companies offer some type of free resources (practice problems, Trial Accounts, videos, etc.) so that you can "test out" a product before you buy it. I suggest that you take advantage of ALL of them, then choose whichever one(s) best match your personality, timeline and budget. There are plenty of sources for practice CATs too (and you can purchase them in 'groups' of CATs).
When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich