Just keep killing and you'll find 'em eventually.
I started grinding for it at lvl 18. Found one at lvl 27. Got the second halfway to lvl 34.
Killed 2998 trainers. Masters around 1.5k.
To make things quick I changed monsters' attack speed to instant and disabled the 'confirm attack' to auto attack when at close quarters.
I also used the 'load and kill' trick while waiting for areas to reset. Got the second ring w/ this...
You can speed up grinding by:
1) Turning your Combat speed to Instant (No Animations)
2) Turning off confirm attack
3) Turning off Display Loot
4) Using the D-pad to attack
Save / Reload does result in you loosing the XP and Gold gained while grinding but when done properly can make getting a Legendary items happen a lot faster.
2 saves: One is after cleaning up the rooms and just waiting, the other is for kill/load.
Just check up on the first save if areas have reset and just do kill/load on the last enemy, w/c is commonly a gargoyle master.
after reading this entire thread that started more than 2 and a half years ago, it feels like finding a RolS to see that there are still people grinding for this mystical ring. I am one of them:
Trainers: 912
Masters: 613
Stones: 386
Gems: 173
Rubys: 532 ...I know, nothing in comparison to what others have achieved. But we all started one day.