I do a very similar distance daily into DC (14.5 miles) and I don't ever wear cycling specific clothing....just regular cotton t-shirts, cargo shorts or twill pants, and tennis shoes. It depends on what you like and whether you need to be dressed up for work or not. I work on the water, so I wear blue collar clothes that I don't mind getting messed up
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In the winter I just wear layers of t-shirts and I have long johns under my pants. Nothing fancy here and it works great for me. The trick is to not overdress. If you don't overdress, you don't need to buy clothes that are designed to "wick away" sweat. These clothes typically don't breathe worth a crap (making you hotter) and stink so bad after sweating that I can't stand them.
Learn how to fix a flat - that's the most common thing you'll run into in terms of issues.
Give it a try and see how it works for you!