I hope I am not asking to many questions.
http://imgur.com/a/U1T4q
This image recommends equiping military dwarves in a certain order, can someone explain that more to me? how do i make them equip in a certain order
Ignore that part. It's based on a combination of (a) Older version of game, (b) Improper understanding of how equpiment weight affects combat and training, and (c) Knowledge partially acquired from adventure mode rather than fortress mode.
Don't give your dwarves 3 mail shirts and 12 cloaks and 17 pairs of mittens and so on. Just be sensible instead. One mail shirt, one helm, one pair of gauntlets, one pair of boots, one greaves or leggings. Maybe add a cloak and a hood (I do that). One shield, and one weapon.
Weighing down your dwarves slows their movement. In 0.34.11 and older, slower movement also means fewer attacks, slower training of skills, etc. EVERYTHING they do is negatively affected. Armor User skill, strength and agility help mitigate that, but there's really not much point in giving them multiple copies of the same armor anyway. It certainly doesn't do enough to overcome the burden (literal) of multiple heavy armors.
In 0.40, attack speed is separate from movement speed, so you
might be able to glean some benefit from multiple armor, but I don't think it has been properly studied yet. (And this isn't the 0.40 thread, so....)