Within your current limitations I think the best way is with a feat found in Lost Empires of Faerun. I forget the name of the feat, but there is one that lets you burn a spell slot one level higher than the normal slot to cast a spell out of a charged item without using the charge. Get a staff with the spell in it (staffs use the better of your caster level or theirs), and a few others you want, and use your slots. You would still need use magic device and some equipment to boost up that skill check (circlet of persuasion). Then you can pick up spells from any list as long as you have the money to buy a staff. Dragon mag free, but campaign specific.