After BCA you can not apply for M.tech through GATE, but for private colleges you need to contact them if they allow you for M.tech.  If you are interested for MCA then it is a good option & MCA is an advanced and more detailed version of BCA course. The program has the topicssuch as Software and Applications Development, Hardware, Networking, Mobile Computing, Computer Science, Programming languages, Algorithm, Internet Technologies etc.

Here are the colleges you can prefer:

Pune University Computer Science Department

School of Computer and Systems Sciences (Jawaharlal Nehru University)

BIT Mesra Department of Computer Science and Engineering

If you want to get admission in NITs then you can apply for NIMCET.

NIMCET Eligibility

 You must be holding graduation degree i.e. BCA/B.Sc (Hons.)/B.Sc/ BIT as per 10+2+3 pattern from a recognised University

You must have studied Mathematics or Statistics or equivalent subject during graduation degree

General category candidates need to score at least 60% marks or 6.5 CGPA score in aggregate of all subjects 

SC/ST category need to obtain at least 55% marks or 6.0 CGPA score on a 10 point scale in aggregate of all subjects

Good Luck!