The answer: a dozen.
The geeky analytical side of me played with some numbers yesterday afternoon. I was thinking on the fact that many of us have more than we can reasonably wear before the item dates rather than actually getting used up and worn out.
For simplicity, I split the year into 2 seasons - warm and cold. I figured a rate of wear at bi-weekly, or once every other week, for each item. Again, this is more for simplicity's sake. Some items will get worn more, some less, obviously. I figured on 6 days of dressing per week, assuming one day is spent in lounge or gear. (this equates to 156 days in a 6 month period)
Ends up we don't need more than a dozen items in any category. And to top that off, at these wear rates, each of those items gets worn 13 times for the year. Yep, that's it. So if a shirt has 52 theoretical wears/washes in it's lifetime you will have that shirt for 4 years if worn every other week for a 6 month season.
For those who don't have a lounge day, figure in dresses, maybe for church. Half a dozen dresses can be worn on your Sundays and still just get 4 or 5 wears in a half year season. Again, that's it! Only 4 or 5 wears. Whew.
For my warm/summer I figured shorts and skirts as bottoms. Understandably, my warm is likely warmer than most lol. No pants in this capsule! 6 skirts and 6 shorts totally covers it with, again, only 13 wears each for the year. None of these items needs repeating more than every other week, or basically twice a month. Say you don't wear skirts? Fine, your 6 shorts will just get weekly wear instead. Or you could expand to a dozen shorts and stay at the minimal 13 wears and bi-weekly repetition.
So, you can have a complete wardrobe, that last for years, and actually wear your items, at no more than a dozen per category, per half year season. That's pretty great. And of course, anything above and beyond all that is just gravy