While it won't fit into the suggestions here because I ride completely casually and clips are definitely more of a PITA than worth it for me, I say get some cheap ones like the Wellgo B087(reflectors just pop off if you don't want them) if you're looking to spend $20ish, or some of the really light, thin pedals available if you've got $50 to spend. I don't remember what model they are, but Wellgo has some really light platforms that aren't very expensive at all. IMO a thin platform pedal looks fine on a road bike as long as the platform isn't too big. Here's a link to the B087 and the Forte Convert. The Convert is definitely a very nice quality pedal and looks better on the bike than it seems like it would in the picture. Since it's very thin it looks nice and sleek on the bike.
Wellgo B087
Forte Convert