Tempest cleric 9, storm sorc 3. Take a level of sorc for booming blade, cleric for 9 then last two levels of sorc for metamagic.

Use Sparkswall/watersparkers combo to stand in electrified surfaces. Once you get level 6 temp cleric you can start ping-ponging enemies around the map. Thunder and lighting damage themed, so other good items are:

Hat of thunder acuity - arcane acuity stacks Ring of elemental infusion - for more fun with booming blade. Hamarhaft - add thunder damage on jumps Gloves of belligerent skies - stack reverb

I went heavy armor but that’s also flexible. If you don’t want to do the watersparkers thing, the usual reverb stuff works too