The OOD plays host to various wardrobes. Really, you can't go wrong regardless of age, occupation, or income.
Within newspaper throwing distance, I've got a guy who wears a silver hard hat, another guy who wears a ruby ring on his pinkie, and that incredibly handsome guy who everybody posts picture of on here.
Personally, I haven't worn a t-shirt since the '08 KU game when a fellow 18er literally ripped my sleeve off in excitement. Since that night, I have moved on to button-downs, untucked. Or, for colder games, button-downs (tucked) with sweater. Purple of course.
Jeans are the obvious choice down below. But, plenty of olds roll out the pleated dockers, turtle-neck combo. risky, i know.