I am in 12'th science c.b.s.c in Maharashtra & live in Gujarat I selected mathematics for engineering & also submitted form 4 jee exam but I am not sure for best scoring in jee,How can I get admission in best engineering college in India,Please guide me.

Hello, the best engineering colleges in India is IIT which you will get through JEE Advance. After IIT, you can go for NIT then BITs then IIIT then Government funded colleges in your state then private colleges in your state. In your state because you can use your home state quota for admission. You can go for other state colleges too but you will go under open category for which the rank cutoff is very low and hard to get.
So as per you score the ran in your jee mains you can go for any college aftet NIT. If you score well in jee mains and appear jee advance and there also your rank is good then you can join IIT at any campus across India.
Hope it helps you