If you're doing short distances/times, whatever's comfy is fine, though as it gets warmer, I'd suggest wicking athletic clothing. For longer distances, definitely invest in a pair of cycling shorts (Lycra, baggy, or a skort, whatever's more comfortable). A jersey with pockets is helpful for holding all your your essentials. Gloves, I think, are a must. They provide a little extra padding if you want it, but the biggest benefit, I think, is that they protect your palms if you crash.