Whats the best way to maximize rewards for gift cards especially Amazon pay?

Hey guys
There are multiple platforms to buy gift cards like Rentpay, Gyftr and Cred etc.
But whats the best platform to maximise the value.

Based on my experience Gyftr gives 16.66% via Infinia but there is a cap of 10k INR of buying it.
Wanted to know the next best platform for vouchers

My primary cards are Infinia and SBI cashback and Amex platinum metal + Rewards