Abjurant Champion is good. Another option is to use armor and shield which have 0% spell failure. Mithral decrease failure chance by 10%. And Twilight ability (Magic Item Compendium, PHB 2, etc.) also decrease falure chance by 10%. So, +X Twilight Mithral Chain Shirt has no spell failure chance.
Also, as you are a mage, increasing AC is not the only way to avoid being hit. Mirror Image and spells which gives use miss chance (say, blur) is often much effective as short duration defense.