IMO playing without shoes can lead to ankle/knee problems later on.
I always have some form of footwear on when I play, although I don't have 'playing gear'.
I feel it's the same as gloves...if one day you happened to forget your gloves, your whole flow is going to be screwed. I don't like relying on stuff like that to help me along.
My preference lies in Vans slip ons, though anything from boots to flip flops is acceptable.
My shoe size is 11, just for comparison. Not monstrous but not tiny.