Is taking admission in a college like TAPMI, GIM and Great Lakes Chennai a good decision or should I drop a year to try for the IIMs?

If you can afford taking a year drop, then definitely go for it and aim for IIMs or other top B-schools such as IIFT, S.P. Jain, FMS. If you do not achieve a higher score than you did this year, you will have to explain what you did with an extra year to not only IIMs, but to every interview you go. However, I would recommend going through the interviews, seeing what you have converted this year, and then make an informed decision.GIM is also a good institute and so is tapmi, but they don't fall in the same category as IIMs though.