As a cleric, the Mercian Crypts may suit you. There's also a quest in there, and if you kill the necromancer, it greatly reduces the amount of specters that keep respawning. If you completed the second quest of that scum Rohl, the one that sends you for a trap, you can get Ruby Key n2, that at least for me was the first and easiest one to grab, so you can already open it. Just check the wiki before to prepare, and beware of the entrance trap. Death Resistance and mostly Fire Damage will do the trick.
Depending on your level, you should try to get to Icemist too by completing the 4 quests of the Mages Guild Enclaves. Icemist has one particularly good quest that will grant you a very good Amulet (Amulet of Whispers or Amulet of Dark Whispers, depending on your choice), and being a Cleric I believe you could do it a bit earlier. If not, there are several other good quests to do, like the one of Lady Xidar (what was the name of the quest again? Damn I forgot).
Usually speaking, doing quests is a better - and less boring - way to improve, in both items, XP, gold and items.
I would recommend you to do Town Hall quests however, just a few, in order to get reputation, if you wanna do the Quest "3 vs 11" (and you do wanna do it), or buy a house in New Garand or in Nivarian (for Ilmaria you'll have to do a few to be able to both buy the house and to gain access to the library)