Kobold Armorer Artificer

Hey, so I'm attempting to design a Kobold Armorer with the gimick of using the Armor to look like a powerful dragonborn, thus making the other Kobolds listen to him. I wanted to give him a lot of cool fire spells that he would cast from the mouth of the suit, like a breath weapon. He's supposed to be a very tanky character overall too. Oh also, my DM let me take Gauntlets of Ogre power and one other item. How would you guys build this character at level 12? Should I do any multiclassing?

I like this idea a lot, it's delightful.

Unfortunately there are not a lot of fire spells (or damage spells in general) on the Artificer list, but Fire Bolt and Dragon's Breath are obvious choices. If this is a 5.5e character, you might want to choose a background that provides the Magic Initiate feat, which would give you access to Burning Hands. You might also consider taking the Elemental Adept feat at some point, as this will let you ignore fire resistance.

If you want to be a tank, you probably want to be using the "Guardian" armor type. In which case it might be worth asking your DM if they'll allow you to (as a house rule) have the armor's "Thunder Pulse" weapon deal fire damage instead of thunder damage, because this would give you a very thematic fire-based melee weapon.