Okay, so basing this cardhouse firmly on the 5 points listed in part 2, here are some rough observations:
Start with a basic silver standard, with names and and values from semi hemi demi roman early empire late republic. (why ? Documentation,similarity to a S&S classic country, and coolness.)
Mix and match for flavor.
Base Coins and names are copper (As), brass or bronze (Sestertius), silver (denarius), gold(Solidus).
Exchange: 1 Solidus = 25 Denarii =100 sesterci =400 As.
or 1 denarii = 4 Sesterci =16 As.
The As can also be cut up or issued in smaller denominations - for game purposes, ignore this. If you don't like bronze coins, a silver sestercii existed, obviously much smaller than the bronze version –or was a cut up denarii. call it a small silver. Most commerce will be conducted in Sestercii and As : bronze (small silver) and copper.
For comparison to later Europe, a denarius was about 3 silver pennies.
A days wage for a laborer (not a craftsman, but not an oaf) = 1 denarius with about 250 days work/year or 250d/year, if work is available fulltime - this was not always the case. A trained soldier would take in about the same per year( before stoppages for food and equipment -oh well.)
A basic oaf or unskilled labor would probably cost half that. A base grunt level soldier would be somewhere in between depending on seniority/status.
Yearly food expenses for a city dwelling family of 4 would be about 200d/year (less as one gets closer to the food sources, but wages are less, too), or about 9 As per day. Rent might be 5-10% of income (50 -100 sestercii/year). These are a bit above bare bones, but not much. So, for the earner (40% consumption) about 80d/year, or ~ 25 sestercii/month or 3-4 As per day. : that gets ya basic bread (2 lbs) + minor amount of cheap veg (onions,pulse,leeks or olives pehaps)+ oil + very cheap beer or horrible wine.
Incidentally, we can see why Rome was so dependent on the dole - without it, living expenses were barely less than income, leaving no room for much of anything else -let alone luxuries (like, a new tunic once a year).
Okay. I've got pages more, but no adventurer is going to be a common laborer or pvt grunt in play. And damn few have dependents (well, except for the tavernkeepers, blacksmiths and hookers). So we can move on, having established the floor values, so to speak.
Next: "How many fine cows for that mail panoply, my good man ?"