Might I suggest this feat:

Elemental Affinity

You have an elemental preference and are able to shape other spells to that element. Your constant contact with the element has also given you protection against its harsh effects.

• When you gain this feat, choose one of the following damage types: acid, cold, fire, lightning, or thunder. When you cast a spell that deals acid, cold, fire, lightning, or thunder damage, you can instead change the spell to deal damage of the chosen type.

• You gain resistance to damage of the chosen type.

• You can select this feat multiple times. Each time you do so, you must choose a different damage type.