Re: Armbands of Dex and Str +2... WTF!? Drop the Dex +2 if the DM is making you pay a ridiculous 8k for the extra bit. That is just disgustingly wasteful. Same for the Natural Armor +2 amulet, 10k for a +2 bonus? It's seriously not even worth the 8k it costs normally.
More bad item picks in there, but that's enough of that... You need more stuff to boost your casting like Metamagic rods, Karma beads, and an Ankh of Ascension.
At your level, your Dex mod to AC is going to matter a lot more than your Armor to AC. Generic Full Plate will let you use your vanilla +1 bonus after scrapping those terrible armbands, and a +1 bonus will let you add some useful mods. At this level, look for Mindarmor and Death Ward (although Mindarmor might not be totally necessary).