Is it a good decision to drop a year, if I am not prepared for JEE exam or not? Should I take admission in any university?

see most of the students who went for jee preparation by droping 1year got depression and no such improvement is saw by them...so take decision very carefully

That depends on your motivation levels and how challenging you take cracking JEE. If you are not much into it, just join any other better engineering college. If you are so determined only then go for dropping an year