I think items are assigned according to order of creation, not order in the uniform. So, you might be able to get a soldier to put on two socks and two boots, but only if those four things were made in the right order.
Usually I assign a 'replace clothing' uniform that includes clothing items. The following uniform results in an appropriate number of gauntlets and boots on each dwarf:
Steel mail shirt
Leather cloak
Leather armour
Steel helm
Leather hood
Leather leggings
Steel gauntlet
Steel high boot
Specific shield
Specific crossbow
Material probably not relevant, but included anyway.
Mail shirt + breastplate is better protection then mail shirt + leath armor - but you're probably going for less weight for w/e reason - marksdwarves are most effective behind fortifications in heavy armor imo, not running around rambo style
Material is relevant - leather is better protection then cloth, and I read somewhere that the dwarves change equip based on item's cost - cloth is usually worth more - I think...
Shield material doesn't change protection, only blunt damg in melee. Quality affect hit chance to a point - same with melee weaps
I personally melt all items below exceptional quality out of arrogance and elitist sentimentality..., so I never have to choose specific items, unless I want Urist McHERO to use artifact "the goblins be bursting" candy Battle Axe
With crossbows, the material only changes blunt damg, the quality affect accuracy. - Bismuth Bronze is best non artifact crossbow material for blunt damg btw
I make 2 sets of "Melee Regalia" uniforms
"Melee Regalia Iron"
"Melee Regalia Steel"
This allows me to send off champions to head other squads, and quickly assign uniform materials to the worthy. Becomes less important as I produce more steel kits though.
Also I have 20/20 steel high boots equipped
20/22 Steel Guantlets equiped - 2 designated for melting, because they did not meet my elitist standards of exceptional +
adding 2 worked for me - but you can chat all you'd like w/out trying it for yourself if that makes ya feel better - won't change it's effectiveness in my forts