Hey Ayush, Train is the best option Bro.... The Indore Duronto express is the best way to travel from Mumbai central to Indore which takes around 12 hours to reach. It runs twice a week, Thursday and Saturday. Visit :- www.irctc.login to book your tickets. Happy Travelling!!!
The approximate distance from Mumbai to Indoor is 585km. Bus :
Travelling time - 14hr
Cost - Rs. 600/- (apx) Train:
Travelling time - 12hr
Cost - Rs. 1100/- (apx) I would like to suggest Bus travelling.