Tool Proficiency: Smith’s Tools allow you to forge your armor.
Armorer Spells: Your specialist spells start out weak but quickly ramp up. The later levels are great.
3rd Level: Solid spells, but somewhat redundant to get two offensive spells. Thunderwave is great since you’re going to be in melee a bunch. You’ve got a reliable ranged attack in magic missile.
5th Level: Shatter is a small upgrade to Thunderwave, but Mirror Image is the better option. Your already formidable AC combined with an additional miss chance makes you nigh unhittable.
9th Level: Lightning bolt!!!
13th Level: Two great buffs. Fire Shield may suffer due to your high AC, but it offers other benefits.
17th Level: A decent utility option and an excellent area control option.
Arcane Armor: This is your core skill. You get heavy armor proficiency, and don’t need high strength to use it! You can apply your artificer infusions until you get the Armor Modifications at level 9. There is one downside…you need to provide the armor. This requires you to buy, build, or win a suit of 1,500 GP Full Plate.
Armor Model: When you gain your armor, you need to choose which armor model you’re going for. Guardian armor is more of a front-line build, and Infiltrator is a more support/ranged role. You can swap your choice whenever you finish a rest, allowing you to change roles pretty easily.
Guardian Armor: This is the go-to option. You’ll find it easy and very straight-forward to play, and fit in well with a fledgling adventuring party.
Thunder Gauntlets: Your punches have standard damage, 1d8, equivalent to a longsword. It’s Thunder damage, so it’s less likely to be resisted than normal weapon damage. Additionally you get to pull aggro from some types of enemies, which is a solid ability given your role as a primary defender.
Combine this ability with a cantrip attack enhancer like booming blade or green flame blade for an extra effect.
Defensive Field: A very deep pool of temporary hit points available to you multiple times per day.
Infiltrator: This armor gives you ranged combat options, and is the preferred mode if you’ve got 14+ Dexterity. This option allows you to use stealth at advantage as well, if you choose breastplate instead of half-plate.
Lightning Launcher: The extra damage only applies to one attack per round. While still outclassing many cantrips, it’s something to remember.
Powered Steps: 5 feet of extra movement.
Dampening Field: Choose Breastplate for stealth, and Full Plate for maximum defense while in this mode.
Extra Attack: This gives you an extra shot with your lightning launcher, but the extra damage only applies once per round
Armor Modifications: Once you get here, you gain the ability to infuse two extra abilities on your armor, giving you more room to share enhancements with your teammates.
Perfected Armor: An additional effect on each armor model.
Guardian: Get over here! The ability to pull enemies towards you effectively gives you melee at range. You can drag a foe through a hazard or spell effect and wallop them when they get to you.
Infiltrator: You’re probably going to be using this armor mode in a stealthy capacity, so getting advantage after the initial attack allows you a second chance to strike after you’ve given away your position. If you tag them again, you can grant the advantage attack to an ally.