Long-sleeved shirt
When the weather is cooler a long-sleeved shirt is ideal. Technical fabrics are a must for keeping the sweat off your skin.
Light jacket
A light jacket over a long-sleeved shirt on cold days will keep you just warm enough. Your best option will be something wind and waterproof, as well.
Tights
Tights or long pants will keep your legs warm when the temperature drops, and the right fabric can provide good sheilding from the wind and rain. When it's extremely cold, a combination of pants over top of tights will give you the most warmth and still keep you comfortable.
Lightweight gloves
A pair of thin gloves will provide just enough warmth for cool temps. Those made with technical fabrics are best, and will do a good job of wicking away sweat. They'll also be easy to stash in a pocket if they end up not being needed.
Reflective gear
Make sure you can be seen at night! Try to wear clothing with reflective surfaces, or get a special reflective vest or wearable LED blinking lights. You're much harder to see at night than you think!
Identification
It's always a good idea to be prepared for possible trouble. Keep some ID on you in case the worst happens. Throw your license or business card in your back pocket, or better yet -- use something like a RoadID that can also contain additional vital information if you're in trouble.
Shop for more on RoadID.com