I've been using this recipe from the wiki. It seems to work fairly well; one legendary armour user/speardwarf stood up to the circus and lasted quite a long time.........:
A bunch of the old wiki templates for uniforms wont work with the latest releases. Caps for one got 'shaped' and dont layer with a helm anymore.
Never underestimate the effects of layering armor. In practice there is room for many multiple pieces, like 6 hoods or 3 mail shirts. I generally dont bother with this, feels unrealistic.
A tweaked version of what xpi0t0s posted that works in latest version but doesnt double pieces:
L Hood, Helm
Mail Shirt, Breastplate, L Robe
Gauntlets, L Mittens
L Trousers, Greaves
Socks, High boots
Shield
The 'L' pieces are leather. Vastly inferior to metal yet less burdening. Still superior to cloth.
You could actually use my uniform as listed above but have 3x mail shirts and 6x robes and it all still fits, I just dont as it looks unreal.
Every extra item increases survivability, you may see in combat reports that your dwarves get injured through 'leather hood' or whatever but in that case the blow is penetrating both hood and helm, only one gets named in the report.
Always set any 'full' uniform to replace clothing or they will equip a random subset of it
edit: when it comes to training off the armor burdens, I give them the leather parts of the above outfit and the metal helm initially. Soon as they hit 2-3 ranks in ArmUser the metal goes back on, this feels to me like just long enough that they dont crawl everywhere. They probably still fight suboptimaly, but that doesnt matter greatly since its balanced by the goblins not being able to wound them even if they do hit. Their armor user goes up rapidly if you make them fight in the plate, it just doesnt work so well if they actually have 0 skill, hence leathers for a year, but it probably take you a year before you have plate for em anyway