Well firslty you are eligible for the JoSAA counseling. So I would recommend you to take part in the JoSAA counseling and fill up as many options you want.

Now consiedring your rank since over 1.5L and that too in a General Category you can't much expect to have a seat in any of the NIT.

So I would recommed yuo to

1. Prepare well for state exams like WBJEE, UPTU and GGSIPU. Trust me, some state colleges (which these exams offer) are far better than bottom 15 NITs

2.  Prepare well for BITSAT for a month. With rigrous study for a month you can expect to have a score 300+. From this you can easily expect a seat from BITS GOA which is better than any of NIT (leaving top 5)