Best ring set after unlimited?

The Imperial Ring from Azwan. Related, so the potential was just wiped from all of them, even if you got one and started cubing it?

I don't know, I've only seen it in the shop. One day it had a red border in the shop, when I checked later, during the Wind Archer revamp, it didn't have one anymore, I'm not sure if it would even have potential if you bought it.

But, if it wasn't supposed to have potential, Nexon would likely wipe it, like when they (NexonKR) accidentally let you get potential on everything a while back.