i'm not sure i fully understand you warfouyn. you're in difficult?
i made two points:
1. your uniforms will work better if you are very specific in what you assign
The uniform screen allows to choose an armor type (that covers a specific area of the body). That can either very general, (say, handwear) or specific (gauntlets, gloves, etc) gloves are a form of handwear, but not all handwear are gloves.
Then you can specify the material type (for instance, gloves can be made of pigtail cloth, rope reed cloth, different types of leather etc), you can specify generally (metal, leather, cloth) or narrowly (copper, which is a form of metal).
This is all very complicated but the most important message is: when you design a uniform be as exact as you can (ask them to find not just any armor but an iron breastplate, not just any boots but copper high boots or whatever you're equipping the dwarf with) and then make sure the uniform is set to "replace clothing". The dwarves will drop the clothing they have (so you don't get issues where the dwarves can equip an item but don't because it won't fit over their current clothing), and pick up the clothing you told them to, if you have it (in the right size and undamaged etc). Dwarves work best when you tell them exactly what to do.
2. The second point is just an observation that this hierachical system of specifying armor type then material gives rise to a few amusing or strange situations. For instance, leather armor is one of the clothing types that can go in the torso section of the uniform (the armor section). It can only be made of leather, but if you want to be specific about what material it should be made of you can specify "leather", leading to a uniform with a piece called "leather, leather armor". If you don;t understand this second point it doesn't matter too much, its more of an interesting tangent.