Arcane thesis feat errata
Conjuration is extremely powerful, and many Conjuration spells work very well for Evokers, especially the low level elemental orb spells and some high-level blast spells. Since Sculpt Spell only modifies the spell's level by one, the rod is extremely cheap.
The other options are mediocre, so 3 levels is plenty. A good option for good-aligned characters because evil outsiders typically have resistance to Acid, Cold, and Fire. Staffs Staffs are very tempting, but their construction rules make them ridiculously expensive.
Evokers and the Evocation school are often decried as a sub-par way to run a Wizard. Only useful if you use Born of Three Thunders, and unfortunately the save DC gets progressively harder as your cast level improves. Evokers don't do well with pets, and they don't really need save or suck spells.
Identity Fluidity of identity was a huge theme in It is also frequently noted that the Conjuration school features many similar, and often better direct damage spells than Evocation. The math for a Maximized spell is actually very good.
The archmage is a phenomenal option for the Evoker. If you have some ridiculous way to boost your Will saves, this might work.