I'd recommend Shimano M324 pedals and a pair of mountain-biking shoes.

The pedal has a clip on one side and a standard pedal on the other. That way you can wear special shoes or regular shoes, it doesn't matter. And, if you need to get going quickly at an intersection and don't have time to click then, you can use the flat side of the pedal.

Non-biking shoes have the clip embedded in the bottom of the shoe so it doesn't stick out onto the pavement. You can walk around in a pair of those just fine, but you do need to be prepared to have elite cyclists laugh at you if you show up for a distance ride wearing a pair... not that this is ever happened to me!