I took too many clothes at the beginning of my first tour. It took me about a week to send most of my clothes home. It turns out I needed very little, see the below list for new tourists:
1. Padded bicycle shorts - Bring three pairs. You should wash a the pair you rode with the previous day, and let it dry on the back rack. Ride with a pair, and have a backup in your rack pack. Make sure the padded shorts fit well and are very comfortable while riding on the bike. Don't wear underwear under the shorts, it will be very uncomfortable.
2. Shirts - Bring three shirts. I do not like cycling jerseys because they don't allow sunlight through, creating an awkward farmers tan. I prefer thin cotton shirts which I washed daily and dry on my rack pack.
3. Socks - Bring three pairs of cycling socks. Cycling socks are super comfortable, thick where you need it and thin where do don't. They work much better than department store socks. Make sure to test your shoes with your cycling socks. My favorite brand of socks is Assos, and I prefer loud colors which will stand out to drivers.
4. Shorts - Bring one pair for hanging out after your daily rides. make sure they are very thin and will dry fast in the sun. I preferred a drawstring baggy short that could fit over my cycling shorts.
5. Windbreaker - A thin windbreaker is required for the cold. Wearing multiple layers, a windbreaker plus two shirts should keep you warn even in extremely cold temperatures. Make sure to tuck in your shirts into your shorts to trap your body heat. My favorite windbreaker is by Assos, it is a visible yellow color, and is long enough to go under my shorts while riding.