The best way to earn Marriott points is on everyone's favorite card Magnus 🙂
Transfer to ITC and then to Bonvoy to get a higher ratio of 5:4:6. This can be done for up to 60000 Green Points per calendar year.
Unfortunately, we don't have any Marriott co-branded credit cards in India. Without those, one of the ways to get Platinum Elite status is going for the Platinum Challenge. This will get you Platinum status if you stay for 16 paid nights within a 90 day period. You can enroll into this challenge by calling Marriott.