Avoid silk shirts without an undershirt. This is a personal view of what women should and should not wear to facilitate the mechanics of Social Dancing, written by a man. The point of view is primarily Swing, but I think the same general ideas apply to all forms of Social Dancing. Leaders and Followers must have quick and easy access to their partners' backs. Therefore sleeves should be cut high into the armpit and not have very loose cloth above the waist line, particularly the upper arms.
Sleeveless tops are just fine, too.
I much prefer fabric that covers the shoulder blades or anywhere else with which I'm likely to have manual contact. I also prefer zippers to buttons because the spaces between buttons are often entered thus allowing contact with slippery skin or bra straps. Garments that expose the stomach are also undesirable for the same reasons as bare backs. Very clothy upper body garments can conceal exactly where we don't want our hands to go on the dance floor. Sometimes dancers I know wear such garments and, if they're wearing a different bra, might not be where I know they were.