Washing of undergarments occurred after every wearing, or sometimes more in hot weather. Women's shifts/chemises cover the arms to the elbow and end below the knee, thus absorbing the sweat and oils that could damage the clothing. Men's shirts function the same way. Into the 19th century these shirts would be very long and tucked between the legs before putting on trousers to serve as underwear as well. Made from linen or wool, these were meant to be cleaned often to keep the wearer healthy. Some surviving examples have initials or numbers stitched on them for laundering purposes. Account books survive noting which numbers were sent to the laundress so there were no mix-ups. The History of Underclothes by Cunnington gives a great overview of what's worn underneath.

Outer garments were cleaned on an as-needed basis. Just like todays suits, they'll be dry cleaned after a season or if stained.

There is no easy way to give numbers for the "average" persons closet, just like today. Some find fashion important, sometimes more so than the consequences of debt. Others, not so much. There has always been a huge range of clothing available, so you could easily choose what you could afford. Prior to the late 19th century, all clothing was custom made. The customer would choose a fabric they could afford and have it made up rather inexpensively so long as there wasn't a great deal of trimming involved. The fabric made up the bigger amount of cost because there were so many people involved in growing, harvesting, spinning, weaving, dyeing, and finishing the textiles than in just sewing it up. Compared to today, if we are comparing to something like Walmart, yes they are more expensive. But if you want a custom made suit today, it's far more expensive than it would have been 200 years ago. A quick example- hand sewing an entire mens early 19th century three piece suit takes about 40-50 hours. So, if you are also a skilled tradesman, it probably is 40-50 hours of your wages for labor. A women's gown from the same time takes 8-10 hours. The sewing machine, patented in 1843 by Elias Howe, reduces these times drastically, but a fine mens suit is still mostly hand-sewn even today.

Fashion is hugely varied because of the custom options. Even when mass production and catalogue ordering become common in the late 19th century there is still a huge variety available. Men's suits become much more stable in the 20th century as they are now really only worn for business or the occasional black-tie event. But that is very recent. Styles and cuts can be fashionable, but that doesn't mean everyone wears that one style in one color with the same fit.