The whole point of cycling clothing is to offer greatly increased comfort over any normal clothing. Even if you look a little dorky. And, thing is, I can ride 20-30 miles in street clothes. So you don't even really need any of them until you are really trying to bike hard and fast and over longer distances.
Sometimes it's more important than others. For example, bike shorts are a huge contribution to comfort while cycling. There are a lot of variants on the design. Sometimes they hold themselves up with an elastic band around the waist. Sometimes they are "bib shorts" that have shoulder straps, which tends to work great for men and not quite as well for some women. They make skorts for women.
The big design point is that it must be comfortably form-fitting yet also not contain any seams in places that will bug your skin. There's a certain amount of individual fit involved. This means that you might like one brand and your buddy may like another brand and, were you to swap shorts (Don't do it! That's gross!) you'd really hate each other's shorts. Shorts are also generally gender-specific.
Bike shorts developed over time. As bikes gained saddles and became safe to ride for long distances, people started adapting existing designs to better serve the cyclists. In the beginning, there were no good flexible stretchy materials, so the standard was some number of panels of knit wool with a piece of chamois leather in the center to make the presence of a seam through the crotch less objectionable.
Even though it's not chamois leather but synthetic materials, there's a breathable padded thing called a "chamois" in between the legs of most bike shorts. There are three vague opinions. Occasionally, folks will insist that it's a leftover from the days of knit wool shorts and seams and entirely unnecessary. Some folks insist that it's there for padding, that it's better than padding the saddle, and that you should have a thick chamois. Other folks insist that it's there to prevent chafing and that you should have a thinner one. Either way, if there's a chamois, it needs to help wick moisture away otherwise it's useless. They make them in all sorts of shapes and forms and at least some of that is marketing, but different folks like their chamois very differently. You can usually get a seam-ripper or a short knife and cut the chamois out.
Modern fabrics can be stretchy, so it's not quite as important to have a bunch of panels to fit. Shorts can be made seamless but still take the correct shape. If the shorts are not meant for your geometry and how you generally position yourself, they won't be comfortable. Under no account should there be a seam in places that will create irritation.
Traditionally, bike shorts used an elastic band around the waist to hold themselves up. However, this is a pressure point and people who have a little extra belly fat will end up with it spilling over the band. Thus, there are also "bib shorts" that use shoulder straps to hold themselves up, which a lot of folks, even skinny folks, prefer.
Now, if you want to bike in the cold, you can get tights that fit like bike shorts but cover the whole leg, or you can get leg-warmers that effectively do the same thing. The nice thing about leg warmers is that they can be taken off mid-ride. You can start the ride with leg-warmers and bike shorts and then take the leg-warmers off when it gets too hot. The downside of leg-warmers is that they sometimes will ride down. You can also get knee-warmers.
Pretty much, if you want to go long distances, you need bike shorts. This is the only piece of biking attire that I will recommend this strongly.
If you are really not wanting to look like a spandex cowboy, they do make "mountain bike" shorts. Basically, it's a pair of normal bike shorts with a matching over-short. So there's nothing preventing you from wearing a pair of normal shorts over bike shorts. Or a skirt. Or anything else. It ends up that most of the hardcore competition mountain bikers don't wear "mountain bike" shorts.
Except for mountain bike shorts, pockets are seldom seen. This is a good thing. Having your keys rub against your leg with every pedal stroke is a great way to get a painful infected boil.
One style point: If a guy rides around in a pair of white shorts, he's going to be displaying a lot more than he realizes. Most men's shorts have at least a black panel to leave the crotch in shadow. There's a picture floating around the Internet to explain that.
On the other hand, the rest of the ensemble is much less of a requirement than you'd think. I biked for a long time with my one pair of bike shorts and a cotton t-shirt. Eventually, because I needed them for riding in colder weather, I ended up with some long-sleeved wicking t-shirts.
I have an argument that isn't necessarily very popular, but I'll make it anyway. Sunscreen is not something you can blindly apply. There is a risk of harm from using it long-term that's fairly minimal, but not zero. Consider the traditional wardrobe from the hotter parts of India or the middle east. People don't wander around in minimalist attire, they are all covered up by light colored lightweight fabric. I think that, for rides when it's not necessarily humid, it's better to wear a lightweight long-sleeved top instead of a short-sleeved top. Modern technology has enhanced our ability to let air through but not UV radiation. I haven't been able to find many jerseys that I knew would be comfortable in the heat, but my long-sleeved wicking t-shirts worked perfectly well most of the time.
Bike jerseys are a great way to cross over from ergonomic to affectation. You can get replica jerseys from your favorite teams and you will see riders who ride so seldom that they've got dust on their frames instead of dirt who feel obligated to wear the correct kit.
On the other hand, I've got bike jerseys these days. So they aren't useless.
The big thing that bike-specific tops try to solve is air-and-moisture-flow. See, if you just rode up a mountain, you've been sweating a lot. If you then descend and have your jersey flapping in the breeze, it's pumping air very quickly past your skin. Which means that you just went from way-too-hot to way-too-cold. The shivers are a great way to have a hard time controlling your bike on a fast descent, mind you.
So, you want to use technical fabrics or wool to let water evaporate without getting wind or rain through. And you want to have the jersey form-fitting such that air can't cause the jersey to billow in and out. This means that people with too much belly fat look really silly in them. Thankfully, by the time I really needed the improved ergonomics of a bike jersey, I slimmed down.
You usually look a little silly standing up with a jersey on because the back is longer than the front. It's designed for a hunched over riding position. This helps you stay modest and not get your butt-crack sunburned.
Bike shorts don't have pockets. Bike jerseys usually do. However, pockets in front will just bounce against your chest or legs while you ride, so you want the pockets to be in the back. Some jerseys have a zippered pocket, but the higher-end jerseys generally have a series of three pockets where each one can hold a water bottle. Some of them even have a pocket for a MP3 player, if you want to offset the increase in life expectancy from exercise by making it hard to hear the car behind you.
Because you put out a lot of sweat going uphill and then encounter a lot of wind going downhill and because most of these materials have a limit to how much they can wick, jerseys usually have a zipper in front. This makes a huge difference in comfort. Long sleeved jerseys have a bit of spandex around the wrists to keep air from going up them. Most jerseys are tight around the neck when zipped up.
Jerseys usually come in sleeveless forms, short-sleeved, and long-sleeved. Long-sleeved jerseys can be thin, for somewhat warm weather, or thick, for really cold weather. Sleeveless jerseys are forbidden in higher-end competition, allegedly because they reduce the room for sponsor logos.
If you join a club or team, there's usually branded jerseys that you can get, to show your allegiance. For a team, it's basically compulsory for you to be seen in your team kit. There's usually a team logo, but also room for sponsor logos. Back in the days of knit wool jerseys, they would need to embroider the logos. Later, synthetic materials let them do dye-diffusion transfers to a jersey, which means that sponsor logos are easily added.
You can also buy replica jerseys from the big teams, which make you slower and pretty much mean that everybody will make fun of you and your silly jersey behind your back. So don't do it.
When William Ware Theiss was designing the outfits for Star Trek TNG, they decided to have a sleek skintight outfit. However, they didn't want the actors and actresses to be obligated to stay in super-trim shape. Thus, they made bright contrasting colored asymetrical panels. This actually works quite well, which is why a good percentage of all non-team bike jerseys look vaguely like something you would see on a science fiction set.
A good bike ride often involves riding up and down hills, potential changes of weather, sudden rainstorms, etc. Thus, you can't assume that you will be necessarily able to pick out an outfit and be comfortable the whole ride. Thus, most folks end up with extra stuff that they can put on or take off, depending on the situation. It's best if you can stuff extra wardrobe in a jersey pocket, so compactness is valuable.
If you've got a short-sleeved jersey and a pair of bike shorts, you can get knee-warmers, leg-warmers, and arm-warmers to cover more skin. With rapidly changing weather, it might be more comfortable to wear a short sleeved jersey and arm-warmers instead of a long-sleeved jersey.
The wicking sort of materials bike jerseys are made from enable your sweat to work properly. This means that if you get caught in a summer thunderstorm, you might be happy in a plain old jersey because, as the water evaporates, it will cool you. However, when it gets cold, getting rained on can become quite uncomfortable. Thus, a rain shell comes in handy, being of a material that sacrifices the ability to wick water to prevent the rain from seeping through. The better rain shells often times have breathing panels with zippers or just a breathable material such that you don't have as much sweat accumulation.
Different sorts of rain shells will give you different results. I've got two and I'll layer them. I've got a rain/wind jacket that works when it's not raining to keep me warm but also will cause water to bead up and run off. I've also got a fairly waterproof rain jacket. I'll wear the second jacket when the rain starts to pour because the rain/wind soft shell jacket will start to let water through. You generally need to experiment.
It takes a lot of rain before your lower body needs anything. This is because, even in the cold, the muscle movements from pedaling are creating quite a bit of extra heat.
Layering also helps to keep you warm. The dead air trapped between layers works quite well as insulation. When it's cold out, I'll wear between two and four layers to keep myself warm and fairly dry. I've got wicking shirts that work as a base layer and help sweat evaporate better.
I tend to think that it's important to insulate the core of the body instead of the extremities. If your torso is cold, the body will sacrifice the warmth of the extremities to keep your internal organs at the right temperature. Thus, a vest can help more than you'd think. The latest style is jackets that convert to vests.
The stingy person in me would like to point out that there's a markup for bike-specific wardrobe. This is somewhat because it's a specialized product with a reduced market space. The advantage is that it tends to fit a cyclist's needs slightly better, having zippers in the right place, fitting better, etc. Also, once you cross over into technical fabrics, even the non-cyclist specific versions tend to get expensive. When my last breathable jacket broke a zipper, I got a more expensive bike-specific version and it does feel more comfortable.
For a few areas, normal wardrobe with separate parts must be dispensed with. For time trials, you can be a little faster with an aerodynamic skinsuit. For cyclocross, there's so much lifting up and down of the bike that you really want a one-piece outfit as well so that it doesn't catch.
Copyright 2007, Ken Wronkiewicz