If the temperature is below 20 degrees Celsius, I wear sweatpants with athletic t-shirt and a windbreaker. In the event of really low temperatures, I also add a long-sleeved shirt and a tubular balaclava (don't really know what it's called).

Anything above 20 Celsius, and I prefer shorts with the above wicking t-shirt -or- a long sleeved shirt if riding in chilly weather.