having a good idea and implementing it right after Btech or after MBA from a good college ? which will be better?
having a good idea is not sufficient to plunge into entrepreneurship.
Successful implementation of any startup idea that will yield both social and monetary benefit is a long journey that as a graduating student, you will not have the financial resolve and professional experience to undertake.
You should first test the waters by taking up employment at a startup or a company of your liking.
Is your idea an offshoot of your Btech education / experience like some AI tool or Electronics innovation ? If so you can implement it in your personal time and show it to investors / friends / family for their feedback.
If your idea is generic and nothing to do with your education (like an UBER / OLA / BigBasket) then you need to prepare yourself for the long haul and first need to get a job and get some experience.
First learn the meaning of hard work and then you can learn to manage money , finances, and big business models involving global / regional sales, service and marketing in a college environment. Those are probably the reasons you must take up an MBA, if you are serious about becoming an entrepreneur.