My first thought is to make sure you start off with Amped Shield and use the block each turn if you would get hit, that gets you three turns of reducing the damage of one hit each turn. And buy scrolls / a wand of Mage Armor. You do not want to take up a Spell-Known slot for it.

Hmm, Automaton has reinforced chassis, but unless you were already planning on having a strength of 16+, that seems less than ideal.

A human can just simply grab armor proficiency at 1st level (Via General Training). If you really want to commit, spend your first general feat to then upgrade it to Medium armor. Watch that Strength requirement for armor though. You might be better off getting the toughness feat for that general feat. Ouch, just realized proficiency does not auto-scale from this feat.

Spending two class feats to get Mountain Stance seems expensive (martial Artist archetype -> Mountain Stance), but does stack with Mage armor.

1 class feat for Sentinal dedication gets you light & medium proficiency up to Expert.

You could be a Well Spring mage, then no one will want to be near you in case you blow up! (just kidding .... or am I?)

That's all I can think of at the moment.