I embark with 2 peasants and with wood training axes or the stuff to make bronze / bis. bronze axes (depending on what I expect is available and what I plan to do. E.g.: if lots of trees, then just 1 training axe or even just 2 logs; 1 for carpenter WS, 1 for the axe to get more logs -- I leave the wagon intact until I unload it bc I think it makes a tacky mess if I take it apart.) The first thing I do is build a cabinet and plop it haphazardly right in the entrance to the fort and assign the 2 peasants to train NONSTOP (they get the best housing as soon as housing is available -- usually a metal statue in the bedroom is enough to make them forget the "enraged by long patrol" or whatever.)
By about 1 - 1.5 yrs in they are elite or almost elite. I've seen 1 unarmored dwarf with a cheap copper axe flay several ironclad ambushes 1 after the other. btw, armor is heavy and slows your dwarfs down. sure it GREATLY increases survivability, but it also increases the survivability of any smart enough to route.
Just be careful about the gobby xbows and bows and try to keep the ratio of gobs to elites less than 1:10 tho usually they kill them in about 2 pages of combat in the logs so they never really fight more than 3 or 4 at any given time before the rest of the gobs' squad arrives. If the dwarf is distracted by fighting he could be hit by a lucky bolt, but most of the time they just dodge or block it (btw I give them shields when I get them -- often wood, but I prefer copper)
As soon as I get 2 elites, I move 1 to another squad and fill both squads to 3 dwarves each -- 1 elite, 2 trainees. They train up pretty quick. If I feel like I have useless peasants, I continue splitting up elite squads into 1:2 learning groups. The rate of military growth increases exponentially, but not nearly as fast as the total population grows. I find that about 10 dwarfs can handle most situations but sometimes I want to go in 5 directions and only have 3 squads. So more squads is more important to me than having many dwarfs in every squad.
The reason I put the cabinet in the entrance is so that they train right next to where they will be needed and they are often the ones to catch thieves. ( kinda like the wiki's recommendation to chain dogs in the entry hallway, but dogs rarely send severed parts sailing.) Since most military skills train agility, they are FAST and fleeing gobs hardly have a chance. When the fort gets rolling and I have time to work on little projects I build a wall in such a way that gob archers have to get pretty close before they can fire at the guards and usually they don't get many shots off -- often times, I don't even have to give orders for them to take care of ambushes and if I do, its usually to rescue a woodcutter or sock chasing noble. I rarely close my fort off from access to the rest of the world -- my defenses are made of flesh, not stone. But I do make choke points. If and when I breach into the caverns then I plop a cabinet down there too. since by that time I definitely have at least 2 squads.
When I get around to armor, I get everyone a helmet ASAP. Then shields, breastplates, greaves, boots, gauntlets. In that order. Reason for helmets is in case someone "gives in to pain." If any peasant gob walks up to him with a wooden stick or a sock, then every hit goes directly to the head. Shields are wonderful for saving your dwarfs, but by this point most have wood already, I just upgrade to copper or whatever is available. Greaves and boots, because I would rather have dwarfs missing a hand than dwarfs moving VERY slow on crutches until they get to legendary crutch walker (which, btw, isn't bad since it contributes to attributes). Then gauntlets just to finish out the suit. I never really finish making armor (bc of metal scarcity) until either everyone has masterwork pieces or all the accessible good stuff is exhausted. I never sell excess metal -- I always melt it.
If I do archers at all (and I often do because of FB rot breath) I check to see if there are untamed animals wandering the map. If there are, then I just recruit a few hunters and a bone carver. If not, then I build archery ranges (about 1 per recruit) and wooden bolts. If not much wood, then I don't do archers. I rarely make metal bolts because I turn metal rarity up quit a bit (bc I like to build my bedrooms out of uniform marble layers and veins can be ugly). But if I have excess then I only build metal bolts to train weaponsmiths. Either way, when they get elite, then I cycle them out from "training / hunting" to "patrolling" and put them in key gobby escape routs / approaches to help soften up intruders before they get to the melee kill zone or to cripple escapees. I build "towers" that are accessible only from underground / inside the fort. I use burrows / schedules to keep them where I want them. and give them TONES of bolts. Both designated in the ammunition screen and in smallish stockpiles nearby the towers. I put bolt production on repeat and let the workshops get cluttered when the (small) stockpiles are full so I don't have to be bothered with managing too much bin production. This requires that whoever makes bolts is completely dedicated to bolt production bc I can't rely on him to do anything else in a timely manner.
I honor military personnel with extravagant rooms and platinum statued tombs, but I mostly consider any one individual dwarf expendable and I don't mind sending them into danger. They were volunteered into the army, after all, weren't they? But they are responsible for the success of the whole fort so I am pretty careful with them. I go through a quite few crutches every year, and I don't know if some of them get much use out of their shields anymore... but it works fairly well so far.
Eventually I'll trade with the gobs long enough to get enough iron to get full steel equipment (or get lucky on an embark), but most of the older soldiers will be attached to their crappy axes by then. Or even named them. Sometimes the gobs don't have iron so I gotta trade for it from the others, but they don't give it up as cheap. Sometimes no one has iron so I gotta put up with hell.