For pretty much any length trip: one pair of mtb shorts; two pair of underwear for riding (I've ditched padded shorts. In the evening I rinse out / wash the pair I rode that day, squeeze water out and then roll into and wring in a travel towel, hang in the tent to dry); two short sleeve and one long sleeve riding shirts (Merino. Launder as the underwear); two pair riding socks (Merino. Wash as needed). Beyond that I bring long pants to ride in the rain or in the evening/morning if it's cool (I've ditched rain pants, and instead I use a pair of Mountain Equipment Ibex Pants. They're very water repellent, and if they wet out they keep me warm enough), a pair of shorts for warmer weather, a long sleeve bug shirt, a rain/wind shell (Rab Latok Alpine), a light insulating jacket (Patagonia Nano Puff or Mont Bell down jacket, depending on how wet I expect it to be), pair of light fleece gloves and light gore tex shell mittens, two pair socks for off the bike, shoes or sandals for off the bike. It reads like a long list, but it's pretty minimal. And, of course, there are some trips when I can leave behind the cooler weather gear.