Hii..

These all three colleges are best in themselves..IITRAM is a government college in Gujarat so it's fee will affordable .while nirma and manipal are expensive colleges .

As the same time nirma and manipal campus may large in size with best facilities .if Candidates want to choose mechanical,electrical,civil branches ones should choose IITRAM .but if you want to choose CS,ECE etc you must choose nirma and manipal University.

In short all three are good in one and another way ..but as you mentioned you are from Gujarat and you want to take Mechanical engineering then IITRAM will better for you.

All the best!!