Serious bicycle riders get a lot of catcalls about their costumes, but the designs are almost purely functional. Whether your biking involves lengthy tours or only an occassional round trip of a mile or so, there is reason for you to go and dress likewise.
Gloves, for example, have two functions. Good gloves are well padded in the palm to ease pressure on the nerve at the base of the thumb when you're riding with both hands on top of the handlebars, and to protect your hands against "road rash." During a long ride, you should shift your hands frequently to relieve the cramping strain. Gloves contribute significantly to hand comfort over the long haul; one trip with them will demonstrate the difference. Everyone, no matter how skilled and experienced, sooner or later takes a tumble. The natural tendency on the way down is to stick your hand out to break the fall. Even if you're moving slowly, you're going to skin up your palm. If you're barreling downhill at 20 or 30 miles an hour and hit some loose gravel on a turn, you could literally lose the whole palm of your hand, in addition to other patches of skin here and there. You can make it home with road rash on your legs, hips and arms, maybe, but it's tough going when you can't hang on to the handlebars. Wear gloves.
The most obvious item of the costume is the bright-colored jersey, and that pretty well sums up the argument for wearing it. It makes you easy to see on the road, day or night. A bike jersey just can't be too garish; the wilder the better. It has other functions, too, including a handy set of pockets across the lower back for a map, hankerchief, a spare tube and a couple of tire irons, a candy bar or whatever. While my daughter was living in Europe, I used to stick a small cassette recorder back there, hang a microphone around my neck, and chat as I rode to the office. Jerseys are made from many materials but the best for all-purpose riding is wool, because of its ability to absorb rain. And sweat. You should have at least two or three. If there's a bikie in the family, they make good gifts.
Shorts, like jerseys, are made from different materials but the most popular is wool. I have a pair of cotton ones that look like hiking shorts, full of pockets, that I wear when knocking around town. On long rides, however, I go to wool. Bike shorts have a chamois insert sewn in the crotch, its function to relieve chafing and irritation caused by the saddle. You wear them next to the skin, without underwear. The latter would restore the chafing problem by canceling out the chamois. Full-length tights also should be fitted with the chamois insert, but made of nylon for the fast-drying qualities advantageous in cold and rainy weather.
Your gear isn't complete without bike shoes. On a long ride they're the best friends you feet could have. The $7.97 discount specials are not suitable for long-distance riding because their soft, flexible soles do not provide adequate support. Bike shoes have stiffeners to take the pain out of pushing on those pedals mile after mile. Good bike shoes are not for walking around in, because that sort of flexing thakes the stiffness out of the sole and reduces its effectiveness. If a lot of walking is part of your trip plan, take along a pair of sneakers. Bike shoes should fit snugly. One of the most important considerations is room at the toe: Your foot will tend to shove forward, and lack of room there will cut the circulation in your toes. When buying shoes wear the socks you'll be riding in, and be picky about the fit.
You may need a helmet only once, but when you need it you need it bad. Those trendy little caps with prestigious bike names on them will keep the hair out of your eyes, but the idea is to keep your brains off of the pavement. Get a good helmet.