You buy a cute ring (on sale, no less), only to find out after a day of wearing it that it’s turned your finger green and the metal coating has begun to tarnish. To prevent this from happening, all you need is some clear nail polish. Simply paint it on the inside of the ring and possibly on the sides where your other fingers will come into contact with it. You might want to reapply after a few months, depending on how often yo wear the piece.
I do this with all the rings (and some bracelets) I buy at trendy stores like Forever 21, Charming Charlie, H&M, etc. Not only does it preserve your jewelry, but it saves you from having to buy more rings to replace tarnished ones. Bonus!