It was sadly all too common in a feuldal system for the poorest folk to own nothing more than the clothes on their back. But most people, even peasants, weren't quite that poor. People usually had at least two sets of clothes: everyday wear and the equivalent of "Sunday best," which would not only be worn to church (at least once a week, often more frequently) but to social events, as well. Virtually every woman, and many men, were capable of sewing, if only just a little, and garments were patched and mended for years. Garments and good linen undergarments were even bequeathed to heirs or donated to the poor when their owner died.
More prosperous peasants and artisans would often have several suits of clothes and more than one pair of shoes, depending on their needs. But the amount of clothing in any medieval person's wardrobe, even a royal personage, couldn't come near what modern people usually have in their closets today.
https://www.thoughtco.com/european-peasant-dress-1788614
Washing in the Middle Ages. Washing away from the river:
As culture developed, population grew, and cities became booming urban centres, a river bed and a pile of rocks were no longer sufficient for many people. Several items designed to aid with the washing process therefore become commonplace, including large wooden washtubs and dolly-tubs or possing-tubs – tall tubs in which clothes were beaten and stirred with a plunger. Washing in this period could be incredibly physically demanding and was often undertaken by poor servants and washerwomen on an irregular basis in a gruelling process known as the “great wash”. Indeed, the length and intensity of the washing process (the entire thing often took a few days involving a pre-wash, a 24 hour soaking period, a wash that took about 15 hours on account of the need to continually reheat the lye, a further wash of the lye-soaked linen, and finally a rinsing and drying process), coupled with the fact that people took pride in owning enough linen to avoid the need for frequent washes, made it preferable for households to wash everything at the same time every few weeks. It certainly can’t have been an event that the washers of the time looked forward to!
https://thescrubba.com/blogs/news/how-people-used-to-wash-the-fascinating-history-of-laundry