1) Buy APV, Flipkart, Myntra gift cards using Infinia Smartbuy, Amex PT GYFTR, Tata Neu Infinity, etc
2) Use them to buy Gold coin brands such as Tanishq (Mia), Joyalukkas, Kalyan, BRPL, etc from Myntra and Flipkart.
3) Malabar and Joyalukkas GCs also available in AJIO which provides discounts upto 10% for different credit cards. AU cards with activated features works best here.
4) Exchange these GCs at shops for buying jewellery at current market price plus making charges and GST.
5) For Tanishq store, use Tata Neu Infinity card for 5% additional neu coins which can again be used for buying jewellery.
6) For other stores like Malabar, Kalyan and Joyalukkas use Amex PT to make payments towards MC and GST. You will not get MR points but you can easily hit the 4L milestone.
7) If you don't travel much, you can also consider redeeming Infinia points and Amex MR points for Tanishq voucher and use them to buy Jewellery.
8) You can also consider enrolling in a Gold Savings plan such as Malabar Scheme and pay installments via APV if you have more time in your hands.