CAT

Likesh, there are different ways of admission in MBA. Some institutes prefer CAT/XAT/ MAT scores only for admission to MBA course. And to appear for CAT/XAT/MAT etc student needs to have 50% in graduation. But eligibility criteria varies for various Management Institutes or Universities, they can take different %age in graduation along with CAT/ MAT/ XAT scores.
Another way of admission is internal tests or admission criteria of individual Management Institutes or Universities.
Yet another way is of management quota seats.
If you appeared for any of the tests go for admission using that otherwise use your graduation scores for admission in some good private university. Avoid going for management quota seats as they generally are expensive.
In fact there are some universities that also offer scholarships to meritorious students thus making quality education affordable to all.
You can check the websites of some universities for more details.
Good luck.

I would suggest IMS. Here are my reasons to prefer IMS over TIME.
Faculty and Study Material:
IMS has best in class material exhaustively covering all topics. All faculty members are very supportive and experts in their respective areas. This will help in building strong fundamentals.
SIMCAT:
Now, this is something that puts IMS ahead of all. SIMCATs are meticulously designed by experts and toppers. So, they tend to be the closest to actual CAT. TIME's AIMCATs are not recommended as far as closeness to CAT is concerned.
Secondly, analysis provided by SIMCAT is unparellled. Faculty members also help in analysing SIMCATs as this is a very crucial part of CAT preparation.
Lasty, you get almost 40 (proctered+unprotected) something Mock tests. These are more than enough for any serious candidate.