"Regulars" are small squads of 3-4 in full-time training and having barracks near the access tunnels. Steel armor and adamantine helm. Supposed to be using adamantine weapons (except the hammers), but have grown attached to bronze and iron weapons that do well enough. Currently two squads with axes, one with short swords, one with spears, one with silver hammers, and one with crossbows. At this point most of them (except the crossbow unit) are elite or legendary.
"Reserves" are 4-5 squads training up on a schedule (2-in-3 or 1-in-3). Started with leather armor, weapon, and shield, but now have gear the same as the regulars for the most part. Hammer, Sword, Spear and Crossbow squads.
"Guild Squads" are squads with no training schedule for everyone else to practice in their spare time and get to wear clothes rather than run around naked. Leather armor, metal cap, and basic tunic/trousers/gloves/high boots/etc. Might add a mail shirt eventually as well. Hammer, Sword, Spear, Crossbow, Woodcutters training with axes, and the Miners are equipped with picks. Guild squad members are generally the logistics side of the fortress; miners, masons, mechanics, cook, medical staff, core craft and smithing positions.
(I like the 'everyone is conscripted into a squad' approach for two reasons. First, it eventually gets them all some basic military skills - level 2-4 in a weapon, some dodge skill, etc. That might be enough for them to survive a fight, and also makes it easier to convert them into a reservist if necessary. Second, if they are in individual combat training they are not in the statue hall socializing and forming too many friendships that make tantrum spirals worse. Downside is that sometimes they are so busy training that they don't do their main job - which can be annoying. And which is why I periodically take my mayor, broker, or armorer out of their squad.)