Are these "offers" coming through eBay Messages?
I agree that setting the robots to see the words 'gift card' should be possible, since they already sweep for telephone numbers and email addresses.
As a workaround , I would suggest skipping Auctions as a format. They are down to less than 15% of listings, and move to Fixed Price/Immediate Payment Required.
You set the price you want and it stays up for 30 days or until someone actually pays.
I take it that your Exclusions are the countries you have already had scam messages from.
You should realize they don't want the product, they want the gift card codes.
You can Exclude entire continents if you wish. And since new sellers are often attacked by scammers, I would suggest that you not ship internationally (except to the USA) until you have 10 DSRs, know what DSRs are, and understand why they are unimportant.