Water Magic Ring: no visible stat bonus, Increases water magic atk. & magic def.
Wind Magic Ring: SPD +5, Increases speed and wind magic attack.
Earth Magic Ring: no visible stat bonus, Boosts physical def. & earth magic atk.
Thunder Magic Ring: no visible stat bonus, Increases accuracy & thunder magic atk.
Fire Magic Ring: STR +5, Increases strength and fire magic atk.
I checked with a fire ring yesterday, it increases fire spell by 10%, not sure if those rings stack or not though, well if they do stack Jeane's thunder will hurt alot, A affinity plus another 30% boost and 10% magic boost from gear set and possibly alert status(1.5x???) too, wow, magic whoopass time, imagine heavenly thunder dealing 4.5k...