As of now Atlas would be the best option for this. Jewellery isn’t excluded from base or milestone benefits and it will help him achieve gold tier on 7.5L spends as well. Another distinguishing factor would be no locking with any specific airline/hotel as it has plenty of transfer partners. Axis Vistara signature would also be a decent card but it gives reduced benefit post 4.5L spend and ties you to just Vistara.
Only thing to consider here could be the upcoming changes to Atlas credit card - if they go the magnus way and start excluding transaction types and etc then Atlas might not be as rewarding in the near future.
Among the vistara ccs, given the pattern you suggested IDFC Vistara would be better than Axis/SBI variants as it provides 3% base CV points on transactions upto 1L per month and 2% thereafter. Jewellery is not excluded nor is a select category, so you’re good on that front.
Eligibility aside, another good shout would be Diners Black Metal - it gives 3.3% base and 2.5% as milestone on spending Rs. 4L in a calendar quarter. Given the expenses, I think this would be doable and it’s a more no nonsense reward as you get flat 5.8% which can be used across smartbuy for any flight/hotel booking.