Should I take job before doing PGDIE from NITIE or directly apply after my b tech?

It is definitely not necessary for you to have experience before pursuing PGDIE from NITIE. If you are getting any opportunity to pursue PGDIE just after your BTech degree then you should definitely join it.

Generally, most of the students prefer to do an MBA program after 2-3 years of work experience. And this is because most people don’t have a clear idea about their future and after working for years they realize the importance of management in the industry. So, whether you should join or not is up to you. Having working experience will definitely make your profile better. So, choose according to your convenience.