All I have to say is "don't give up even after dying." When I played through FFV and got to the 4 Crystal guardians in Ex-Death's forest, I faced them close to 30-some times. I gave up for a little over 3 months until a friend of mine told me to use the Samurai "$Toss" command and take them all out at once. Got it on the first try after that then. Don't give up.

If at first you dont succeed, rethink your levels and abilities. When you're the right level, there should be no problem. "Auto" skills are your friend. Sorry if that's a no brainer, but I know that it took me a while to realize that. Auto haste, regen, and potion are amazing skills. And your support skills like Antibody, etc. Hope this helped.

Coral Ring can be bought in various shops, and can also be obtained by beating the Festival of the Hunt with Freya in Disk 1. It's a mere add-on which absorbs Thunder-based attacks, and can be equipped by anyone.