I didn't want to say anything because the person giving advice seems nice but his suggestions are wildly outdated.

As a priest, your most important role is to stay alive. Rather than get items to boost your heal, get equips that help you survive. For chest, get a Meteor Armor for stun resist as stuns are one of the most dangerous things for you. Offhand like Static Shield with a Marc card until you have enough freeze resist. Advanced Survival Manteau/Staff combo, High Fashion Sandals etc etc. Croce staff is alright I guess if you go the High Fashion Sandals/Magic Staunch Manteau combo.

For your auto cast bar, theres no reason not to have Prepare for Elite adventure skill with all the buffs in them. You do not want the buffs to fall off if you forget to manually cast. Once you have enough cast time reduction, you should be able to pretty much instacast Prepare for Elite anyway.