You have a head start because your current line of goods is relatively high-value.
Read the Money Back Guarantee carefully. There is (slightly) (very slightly) more protection for sellers there than you might think.
Consider using the Global Shipping Program to extend your sales outside the USA. Again, the MBG is on your side when you ship to a freight forwarder like GSP.
Use Signature Confirmation every time. Even when eBay does not require this. And say so in your description. "For your protection, all shipments are sent with Signature Confirmation of Delivery".
This has the advantage of being true, since the high value package will not be left on the porch for passing pirates to snaffle, but also protects you, not just from INR claims, but also by warning potential scammers that you were not born on a turnip truck.
If you have been able to harvest addresses from your previous purchasers of fine goods, contact them with information about your new line. Someone who bought a Longchamps bag is a good lead for gold earrings.
I don't sell jewelry, or coins, but I often ship postage or single stamps valued over $500- $1000. These practices have been useful.
I will note however, that philatelists are painfully honest, if fussy.
