Other people may put more effort in than me - which is not surprising - so if I put my head to it, and didn't own a million and one Sheffield Wednesday shirts, then maybe I'd come up with a fitting outfit.
My first thought is usually which end am I sitting in? Home or away. This is because if I'm sat in the home end of another team watching my team (because it's cheaper) then I shouldn't wear my teams colours. I avoid the colour blue at all costs, though I still won't wear the colours of the home team.
Once you have a colour theme, you have to think about the weather... skirt, shorts, tights, trousers, jeans or jumper? I don't think about coats as when the adrenaline starts I no longer need a coat.
I tend to wear a skirt and tights or my comfy jeans, it can feel like a long day when you're losing so to be comfy is my priority. I also never dress to go out afterwards; however, I'll always make sure they are clothes that can get me into pubs and clubs just in case though.
I aim to be as comfy as possible so my top is never fitted and tight, it is loose and flowy. I also tend to wear tops that, like my shoes, I don't mind getting drinks spilt on me as when that last minute goal goes in the back of the net whilst someone near you takes a drink... it is game over in more ways than one.