Life on the road is not as glamourous as it sounds - the Hell's Angels can testify on that point. Medieval hygeine wasn't always as frequent as today (some thought King John effete because he bathed weekly) yet in some cultures (like Byzantium or Rome), bathing was expected and in fact the norm among certain classes.
Monthly expenditure is only really applicable to cities, the military and business; depending on where you are and how you measure time. Seasonal movements are better - a pragmatic need to change clothes by weather with shifts in fashion. Besides, if you're het up about the monthly thing, multiply costs by three each season, depending on calendar. Less paperwork, more fun.
Larger excesses may be expected in decadent courts where the jaded and fashion conscious drive up costs. Refusal to pay for this incurs social penalties (ranging from court disapproval to being arrested for tax evasion) - note the lower down the social hierarchy, the stricter the punishment though snubbing court is bad enough for some people.
So every season consider the following:
- Location. City life is more expensive than rural living (people go to the city to seek their fortune after all). Nobles and courtiers pay through the nose for court time and gods save the King, who must outdo everyone. Decadent courts demand outrageous costs to amuse jaded sensibilities even when fashion is your skin decorated in gold leaf knotwork. Equally the northern barbarians don't mind your old bearskin - it's warm and you killed the bear!
- Prices. Royal perogatives (purple, ermine, venison from royal forests and swan) make good story hooks as people inevitably try to profit from or break laws out of necessity. Certain dyes may be valuable (as in treasure) due to hazardous manufacture or far-off origin. Then there's the simple fact of cost and availability to consider; courtier outfits are not always available on demand in a rural village.
- Quality of lifestyle. Cloistered monks have different requirements to courtiers to city watchmen. Soldiers need to repair weapons damaged in duty. Feudal serfs need to pay taxes to their lord and work the land (possibly needing hired help if they're adventuring) or risk becoming outlaw.
On reaching -3 or -4, there should be even more tangible consequences. Those who live in cities may attract disease or incur harassment from gangs or the watch. Those who make some kind of profit from holdings or business will see losses due to their appearance. In court, this may be sneered upon or even worse offend, leading to a quest or charter to clear reputation or at least get the miscreant out of harm's way.