Previously, I have a advocated having about 12 items of socks, underwear and shirts based on the laundry cycle of the typical toploading laundry mat.
This works well, because it allows you do a cold and a warm (60C) wash at the same time every two weeks or so. This works well for a single person. If you’re a couple, you can divide by 2.
However, realize that the size of the wardrobe is strictly limited by how often laundry needs to be done. In the past couple of weeks I have verified the obvious. When I was packaging my luggage for my trip back to my folks, I asked them how often they did laundry. All the time, they replied (smaller washing machine and three adults in the household). Since I would be number 4, I just divided the magic number 12 with 4 and so I brought 3 pairs of underwear, 3 t-shirts, 2 pairs of pants, and 1.5 sweaters (a thin and a thick one) including the ones I am wearing.
The desire to use a washing machine efficiently generates a need to own more clothes. If you handwash or otherwise is able to wash really small loads, it is possible to make do with just one set.
Simply wash your clothes every day before you go to bed and let it dry overnight. This is possible for quick drying fabrics which sadly are rarely natural fibers.