Update:
I've purchased from Kalyan (around 2L) and Joyalukkas (around 3.5-4L).
Both kalyan and Joyalukkas has 2% and 3% off on their gold jewellery gift cards on Amazon which I used for the entire purchase.
I had been hoarding apay and amazon shopping vouchers from oct using infinia and 2 add ons (so 60k a month). Used 1.5-1.6L from here to buy gc.
Also, bought gift cards directly using sbi cb on amazon, got 5% cb on top of that discount. So 1L from here.
I also hold neu infinity and tata neu had 2% neu coins on Amazon shopping vouchers. Purchased 1L from there at effectively 7% cb (2% in neu and 5% in neu card)
Remaining gcs I bought using Amex plat travel and infinia directly on Amazon.
Regarding making charges: Negotiate hard with the jewellers. We were able to effectively get 30% making charge discount in Joyalukkas and 25% in Kalyan.
We didn't like any design in tanishq and it had atleast 5-7% more making charges than the other chains but from past experiences where we were exclusively buying from Tanishq, they don't negotiate much.