Hello yashu.

There are various types of colleges you will be getting through JEE mains.

If you qualify jee mains and afterwards qualify jee advanced also with good rank then you will be getting IITs which are topmost rank colleges in India.

Next based on your JEE mains rank you will be getting other colleges in which NITs are best then comes iiits and CFTIs afterwards some good private colleges.

And you will surely get a good college if you work hard and study intensionaly.

Good luck.