As far as other equipment goes in Rappelz, you want an r2 robe. You should upgrade its defense when you can, but it's not terribly important. You can also get by just fine with only minimally upgraded gloves, boots, helm, belt and so on. You'll rarely be hit, and when you do, a few points difference won't be that significant. It's good to do, but not essential.

Enchanting your robes to +4 with defense cubes is a good idea, because enchanting boosts the MP regen bonus on the robe, where as upgrading at the blacksmith doesn't. If you're choosing, enchant your robes rather than upgrade their level(rappelz rupees) at the smith. Note however that the MP regen bonus you get from this is very small. If your money is tight, this is not a priority. We're talking 2-3 extra MP while sitting, verses your existing 50-65 points per tick. Not a big deal.

Rings/Earring:
Acquire two +4 dex rings. This should be the highest priority after your staff, and possibly even more important than your robe. Why dexterity, because it increases your cast speed, and that's the single most important thing to a cleric. You'll find out why below. Here is the cheapest Rappelz powerleveling.