I suggest every player, no matter what class or build, to get, and use, one and only one rank in support, except for enchancer who need more. Why? Because you will learn Rakukaja, a skill that when used gives you +4 points in physical Def. That is not so great, but its only 1 rank, so i really think anyone should get it. When you dont need it anymore you can just use of the 6 free lethes bottles you can get into the game.
Another good thing is Sukukaja stones, They raise your critical defense and are really cheap, you can buy 20 for 400 macca in magic shop. If you have a build without luck or use a tarot or equip that decrease your luck, you will receive critical non stop, but those stones will help a lot.
Aside of that only armor and vit, but that depends on your build and style and those thing so i wont talk about it.