I've just started the Dawnguard questline, and trying to decide whether to join the vampires or the Dawnguard. I play as a mage character, and know that you get the ring of erudite by becoming a vampire. Is it possible to obtain a better ring for mages in the game, or perhaps possible to enchant a better ring yourself?

Is it also possible to give the vampire royal armor better magic enchantments than the Archmage's robes?