for an FS priest, max int and use a bacsojin card (heal and sanctuary +30%). I would completely forget DEX and go full VIT and use any leftover points into LUK (because a little p-dodge makes more sense than a tiny amount of flee).
So recommended equip:
Headgear cards: Bacsojin
Armor: Peco Peco... unless you can get a Tao Gunka.
*Incubus and Succubus would be a good combo, but don't use them separately.
Weapon: a 4s rod with 4 Fabre cards is as good as anything. and cheap.
Shield: Andre Egg card. Enchanted Peach Tree could be handy. If you have the cash, buy a bunch of "reduce damage from" cards and switch them around depending on what you're fighting. otherwise, andre egg is fine.
Garment: Giant Whisper. Or again, go for "reduce damage from" cards.
Footgear: Honestly I love Amon Ra. There's a lot you could put here; footgear has great cards.
*Dark Lord and Dark Illusion set would be excellent, if you can get slotted upper, mid, and lower gears. Then you can have Bacsojin, Dark Illusion, and Incubus. Which would be awesome.
Green Ferus, Matyr, Merman, Verit, and Zombie would all be good.
Anyways hopefully that helps a little bit.