Well it has been a full year since I began taking barre classes en-male but while wearing all women's clothes, solid color leggings, tank top and grippy socks. I love the atmosphere, devoid of testosterone (except for mine) and such great encouragement toward each other. All of the many studios have been very welcoming and they all suggested that leggings (no need for shorts over them) and a tank are ideal along with the sticky socks. I have recently added shiny black leggings and semi-fitted tanks.
The instructors are great and they expect/encourage me to do the exercises just like my classmates, legs stick straight, toes pointed and all done with graceful movements. It is so fulfilling to be able to show the part of me that likes doing ballerina-like exercises obviously designed for women and being fine doing it in women's active-wear.
If you want to give it a try I encourage you to do so. If you have questions ask here or PM me.