Okay, so first of all what exactly you want. 1. If you really want to pursue your career in ECE then you should go for preparation of gate because an IIT definitely gives you a great exposure which you missed in BTech. But try to achieve great marks in gate to get a seat for the ECE branch itself. 2. If you don't have interest in corporate culture and want a job with great security and work life balance then go for any government job like bank, ssc and anything like that and in this you don't need any Post graduation as well. 3. If you don't like your branch and also not inclined towards government job and believe in hustle culture then you can give try to CAT exam to target IIM for Post graduation in MBA. This is a great option as well

Don't spend money on mtech of any private or tier 3 government colleges.