« on: April 22, 2012, 11:08:15 pm »
There's a lot of room for personal preference here. But I'll respond as if you had asked about the least amount of clothes you can get away with.
You need one pair of on-bike clothes. For most people, this is a pair of bike shorts, a jersey and a pair of socks. I think most people would take a second pair of socks and a second pair of shorts so that they could rinse out a set each night and be sure of having a dry pair in the morning, or have a clean pair in case you don't have enough water to rinse them out.
You need one pair of off-bike clothes. This means a shirt, a pair of pants, socks and underwear. If your pants have zip-off legs, you can make them do for both long and short pants. If you use cycling shoes to ride, you probably also want a lightweight pair of shoes, which might just be sandals or flip-flops.
Most people want some sort of protection from the rain. A lightweight rain jacket will do. Some people like rain pants too, but many people do not take a pair.
Everything else depends on how cold it will get on your trip. Get the average highs and lows for the places you will go through. I wouldn't worry much about record highs and lows, since you can't prepare for everything. I like to figure out what the coldest expected temperature will be and then take enough clothes so that I'll be okay if I put all the clothes I brought (cycling and non-cycling) on at the same time.