My friend got admission in the FMS and he is still thinking of dropping a year to get admission in the IIM Ahmedabad, Bangalore or Calcutta. What should he do?

Well, it entirely depends upon your friend and his professional profile.

He can think of a reattempt if:

1. He has a great academic record in X, XII, and graduation 
2. He has a work experience of at least 2 years at present.
3. He is confident of scoring high enough to get a call from IIM A, B, C next year and convert at least one of them successfully.

However, he should thoroughly evaluate his chances of being successful in securing his place in either IIM A, B, or C. Also, will his/her profile be good enough next year? With the admission criteria changing every year, it's not advisable to drop an offer from one of the premier non-IIM B- Schools for CAT retake. The cost of dropping a year in terms of money, time, and work experience, in particular, should be thoroughly evaluated. 

Drop a year only after careful consideration. Otherwise, it will be wise to join FMS and give MBA a shot.