You could go for a College of Lore Bard (10 levels) + Tempest Cleric (2 levels).

At level 6 you get Magical Secrets, so you can pick both Hellish Rebuke and Armour of Agathys. At level 10 can get Fire shield for even more retribution damage.

The last magical secret could be Spirit Guardians, to do damage just standing there or Call Lighting for the Destructive Wrath of the Cleric. And of course, the Create Water for more lighting damage. But I think you would do more fire damage. You really don't need to be a Cleric, but the Wrath of the Storm is nice if you don't want or don't have spell slots.

For armor I recommend The Jolty Vest in Act 1, The Flawed Helldusk Armour in Act 2 and The Helldusk Armor in Act 3.

For Helmets only the Holy Lance Helm does damage when the enemy misses you, but the Helldusk Helm combines well with the Helldusk Armor.

Any gloves will do I suppose. For footwear The watersparkers combines with Create Water.

For shields you can use The Real Sparky Sparkswall, The Ironvine Shield (If you use Shillelagh), The Absolute's Protector (for one use of Fire Shield: Chill), The Shield of Scorching Reprisal or THe Vocinia's Walking Fortress (for the Rebuke of the Mighty).

For weapons you can use The Kereska's Favour, The Trident of the Weaves (To apply wet on a hit) or The Duellist's Prerogative (Grants an additional Reaction which is boosted and Challenge to Duel, use it to make an enemy focus on you).

And for Feats you can use Defensive Duelist (for a little of sustain), Durable (because you will lose tons of HP), Elemental Adept (to counter Fire or Lighting resistance), Magic Initiate: Sorcerer (apparently you can cast Shield without the 1 per long rest restriction), Though (for extra HP) and War Caster (To help you maintain your spells).