I have been ruminating over how one could make the economy work. I believe I've put in the idea of a bank before and I shall do so again, along with some other ideas.
DF banks, at least for now, will not really be banks. That is to say, they will not do what banks usually do today: make loans and deal in interest. Right now they're deposit boxes, and their main purpose is to make the economy run with fewer hitches. Back in 40d, dwarves carried coins around, and the algorithm had the unintentional side effect of making them break them down into smaller and smaller stacks, which could bring a fort to a standstill.
It'd probably be difficult to redo the algorithm to do what we want it to do, so why not find an alternative?
Banks are run by bankers. When the economy kicks in, at 20 dwarves I think it is, you will need to build a bank and appoint a banker. The bank can be built from a chest, a table, and a chair, as well as a piece of stone or wood or whatever.
The banker acts as a sort of extra bookkeeper in the bank. He's required for the bank to run, but about all he can do is manage the accounts and make a mandate for more coins to be minted. As your fortress grows, it may be a good idea to open other bank outlets and appoint staff for them.
Now we get to talk about guilds, which used to exist. Here are my ideas.
A guild can be formed from a certain industry once there's 20 dwarves, at least 3 members of that industry (any less and the guild will be more of a tax than a help to the fort), and they don't have a grudge between them if there's a relatively small number of them (which would hinder the formation of the guild). There must also be a perceived need for representation. If your mechanics are getting work, selling their wares to the shop and depot (more on that in a bit) and running a bit more than a living wage, have enough workshops, and don't run out of raw materials, they very likely won't feel that their industry needs a special interest group. If one of these things is lacking, however, bring on the RNG to generate chances that they do form a guild.
If they do form a guild, they will attempt to include all dwarves whose highest profession is in that job, save for, perhaps, a well-hated member of the group. If their work is in demand, they will add new jobs; if their work suddenly falls off then the least-experienced members will be dropped off the list.
Guilds can make mandates. This may involve...
-building new workshops
-increasing raw materials
-selling more of their products by caravan
Guilds rely on each other. Certain raw materials, specifically bones and raw stone, cost nothing, but most others do, and they are bought from the guild that made them. The guild then works on them, then sells their product on to another guild for further processing, or to the broker for sale, or to the shop for sale to other dwarves. The money they make is then split among them with the purpose of giving everybody 120% of the money needed for food, booze, clothing and rent, any extra being saved in the guild office.
As for civilian clothing (haven't gotten to military yet): a dwarf can wear 1 piece of clothing in each slot, and when it becomes a xxclothingxx he goes to the shop and buys a new one with his own money, throwing the old one away.