[SunilNagpal]

As per your interests, GATE is a must. Followed by that give priority to GRE and then DBT/CSIR UGC NET.

Apply for the same for Jan intake of the next year (after clearing GATE) or anytime after GRE.

Going by your interest in stem cell research, MBA wont be a good option. NUS MBA PhD program is very famous, but you might not find a suitable project to satiate your interest in stem cells.

Ideally, you should pursue masters from an IIT/IISc and then pitch for PhD abroad.

Let me know if you have any other queries.

Best wishes