Barefoot here, with G25. Socks slide about too much, and the G25 pedal set up is not robust enough for use with shoes....ie you can stomp on the hard like you can in a real car.
Well, I do wear racing gloves when using the DFGT; mostly because that way sweat doesn't get in the way, my hands stay nice and cool and I have a lot of grip, plus I wan't to spare my hands because I have FFB always at 10.