Congrats you have got a good rank PGECET, But with this rank it is not easy to get seat in JNTU-K, your rank is beyond the rank list. So its better to select other universities and colleges for your Mtech and for your rank you will get seat in top colleges in AP. The best specialization for doing Mtech in ECE is  Embebded systems, VLSI, Communication and IT Engineering, Robotics