There are some buyer requirements that you can set at
You can block known bad buyers and stop buyers who might have cancelled other purchases that they never followed through on.
You can set the Immediate Payment option on Buy It Now listings so that items aren’t actually sold until payment is received. This isn’t an option for auctions.
Anything that is high value should be sent with Signature Confirmation. Sometimes, just stating in your listing that you will ship with Signature Confirmation will deter scammers.
Remember that even though you can say there are no returns allowed, there are always returns allowed. The SNAD (Significantly Not As Described) return option is always available to all buyers regardless of whether or not the seller states that they accept returns or not.
If there is an issue, make buyers return everything and make it as easy for them to return as possible (i.e. send them a return label). Scammers will expect sellers to fight returns and that puts sellers in a bad light with eBay when an issue is escalated to them as they are the ultimate judge. You don’t want eBay to refund the buyer and let them also keep the item.
Always be professional in any communication with a buyer who has an issue and only communicate through eBay Messages. eBay sees these messages and can use them in determining your case.
Unfortunately, you will have to accept that scammers will be able scam you the first few times that they try. eBay will side with buyers for the first few times that there are issues until a pattern of bad behavior exists.