You can bike in almost any clothing. If I am going out for a ride ride I wear bike clothing - it's just more comfortable. When I have biked to a store, I have worn regular clothes. I'm lucky when it comes to commuting because I work in a bike store during the summer, so it's bike clothes to ride to work in and then I change into reg. clothing and nobody minds if I was sweaty because I'm among like minded people.

A while back I came across a blog by a young man who would go the thrift stores and buy old wool trousers that he would then cut & sew into shorts. He would wear them to both toodle around town in & to mountain bike. They looked really cool.
I also remember seeing another guy who bought old shirts from thrift stores for a couple of bucks that he wore to ride in. Short sleeve for summer & long sleeve for winter.
If I remember correctly, the guy who made the short s just liked the recycling idea, and the guy who wore the shirts was on a tight budget.
Maybe inexpensive clothing to ride to work and then change into the good stuff.