It depends on a variety of factors including your lifestyle, the climate where you live and/or travel, your job, etc. I would say a week's supply of everything plus 2, except undies and socks. I would say minimum 10 pairs of underwear and socks. At least 3 bras.

If you work out, you probably want fresh clothes for that. You would need enough clothes for however many times you work out in a week. You also probably need more socks for working out.

If you swim, you need gear for that.

If you attend religious services, you need clothes for that.

You need work clothes. Preferably the kind you can mix and match so you don't look like you were the exact same outfits every week.

You need casual clothes. For some folks that is jeans or shorts or leggings or dresses or skirts or something. Again, a week plus 2. If you go on vacation or it is a holiday or something, you should have enough to go without doing laundry every few days.

Weather gear: if you live somewhere with a lot of rain, probably a rain jacket. If there is snow, you want a thick coat. If it gets chilly but not crazy, maybe a medium weight jacket.

You need clothes for a funeral. If somebody dies, you don't want to be figuring that out while you are grieving.

Shoes. 2 pairs of work shoes, at least one pair of non-work shoes and if you work out minimally 2 pairs of workout shoes. Also, if you live where there is snow, at least one pair of boots.

Pajamas. Again, a week plus 2.