My wardrobe has been slowly shrinking for some time. I never lacked for clothing, and I realised some time ago that I never wore most of the clothes I owned. This is still true to some degree, and is something I'm working on. There is, logically, a minimum amount of clothing required to go about your daily life while still ensuring that style and social obligation are catered for. You can only wear so many smart shirts to work over the course of a week, for example. You need a surplus to deal with unexpected circumstance. You need to account for the weather. You need to account for sports, hobbies and social activities. The list of things that we dress for is not insignificant, but the overlap allows for items in a wardrobe to be multipurpose.
My wardrobe itself has also been getting the minimalist treatment. I had a chest of drawers shoved in there of which only one drawer was actually used. Now there's an organiser hanging from the shirt rail and it's filled as well as more easily accessible. It's a little change, and it makes a little bit of difference every morning.
I came across Project 333 a little while ago, which while not entirely suitable for me, is absolutely along the lines I've been thinking. I don't have a seasonal wardrobe, I am not in any way fashionable, I don't need to rotate items through the year. If I look at a similar limit on the number of items however I think I'd be on the right track.
I have a small collection of nerdy t-shirts that I may have to make an allowance for, but the oldest and smallest of which are likely ready to be cycled out of use anyway. Even considering this, I reckon I can get down to about 30 items discounting underwear. That's the challenge, and as I replace older clothes I plan to clear out and reduce parts of my wardrobe accordingly.