Most of my stuff is groundeffect MTB http://www.groundeffect.co.nz/ stuff, I don't have the bod for skin-tight lycra stuff, and I don't think its appropaite to be going around with your penis practically on display in the office either. But everything I wear is cycling-clothing, I wear bibs but underneath a pair of MTB shorts. On short runs, (tough as the nearest supermarket/pub is about 5 miles away), I may wear cotton but not often, its usually GE as it can be worn out and about, away from the bikes.

I started off in jeans or normal shorts, and cotton t-shirts on my 7 mile one way commute back in the UK but quickly found that they were pretty horrible particularly if it was raining. My cotton t-shirts would be destroyed by deoderant+sweat stains. I hated feeling sweaty or wet in weird smelling jeans from the rain. Sitting in college in damp jeans that feel like you have a band of razor blades locked around the scrotum - no thanks you!

I soon moved away from normal clothing. Cycling clothing is made for a reason and that it is better than normal clothes for cycling.

Clipless - my cycling life improved immensely when I switched to clipless.