I've been dealing with something similar because of the summer-fall seasonal job I am working at again this year - I have to wear a particular t-shirt on Saturdays, but can wear anything within the dress code (basically no t-shirts with logos, no distressed jeans, no leggings, and closed-toe shoes) on other days. But it's a quite physical job where you can get sweaty and dirty and are always moving around, so I find that most of the 'interesting but still within dress code' options I've tried have ended up failing the practicality test.
For a while this summer it really irritated me because I wanted to somehow express my own style but still be set to do my job well. As it gets into fall we get busier and a larger proportion of the staff wear company tees every day even though it's not mandatory, just to make it easier on customers and our new coworkers who don't know everyone, I guess. I've started doing the same and have a 'uniform' of the same tees and bottoms that I cycle through, which has been OK with me. Maybe it's what someone said upthread, that if it's clearly a uniform I don't worry that anyone will think it's my own style and judge me on it.
(I will be a contrarian and say I don't like the idea of school uniforms. I never had to wear one and I would have hated it. My clothes were one of the few ways that I had to express myself in that environment. And socioeconomic difference between students is always obvious anyway.)
