Skill, strength, and technique are all important aspects of climbing; but what you wear may also influence your performance. You might be wearing pants that are too tight, your shorts might have been stuck with the leg loops of the harness, or you might have opted for a cotton shirt and now it's drenched with sweat, you can feel the weight wearing you down. There is no formal outfit for climbing, since each person has their own preferences, but here is a quick guide on what is best to use.
Indoor sports climbing
For guys, the choice if you should wear shorts or pants is definitely up to you. If you're wearing loose shorts though, opt for those with tight inside so when you climb up, your sensitive areas are protected from the view below. Shorts, however, do not give your legs protection from scrapes and bruises on your knees since your skin can be in direct contact with the wall, but the breezy feeling is comforting. Those who prefer pants have some advantages: their legs are safer from the scratches and it is way less painful to put kneebars. Remember to pick those that have the extra stretch in a crotch, so that you are still able to do high steps. Some climbers slimb in special climbing jeans as the fabric gives an extra protection and takes a lot of wear.
For tops, the range is very wast from tank tops, shirts, and long sleeves. Quick-dry fabrics are best of course, so opt for textiles that are meant for athletic use. As we use chalk, black color might not always be the best idea for your clothes.
Climbing without a top, only in your shorts and shoes, is a trademark of most of the top climbers. They say that the weight of the t-shirt "weights them down" during the hard ascents. It makes sence, right?
For girls, the idea is pretty much the same. Opt for clothes that you are most comfortable with, and also something that is suitable for climbing. Yoga pants or sports leggings are great for climbing, since they give your legs protection, they are smart fit, and they are crested for activities that require a lot of movement. Shorts are okay too, but make sure when they are fit and secure - they have a tendency to roll up especially when you wear your harness. For tops, wear your most trusted sports bra underneath a tank top or a shirt. Some would wear an old loose shirts which are fine, but make sure it's not too loose since it might be dangling around and getting caught in your harness.
Outdoor sports climbing
When climbing outdoors, always be aware of the current weather conditions. If it's winter season, always bring a down jacket to keep yourself warm (and also keep your backpack light). Best down jackets have a zipper that can be unzipped from the bottom as well. This makes it so much easier to belay! The sun is high and dry? Go sleeveless and show off the biceps you've been using hard. Doing a multi-pitch route? Wear your most comfortable clothes and rainjacket since it will be a long way up. Remember to be better prepared than sorry.
If you want to climb outdoors and it's cold, there is a few valuable tips: bring a warm par of gloves, as it gets really cold while belaying. Climbing shoes can get really cold and unfomfortable just laying around while you belay, so tuck them under your warm jacket.
Gear to wear
Climbers have specially designed shoes that are suitable for the sport. These come in different colors, styles, and sizes, and you can check the guide on how to pick them here. Climbing shoes are meant to be worn with no socks (yes, sorry) so make sure you clean your pair regularly. A chalk bag is on every climber's waist, and you should have your own by now. Remember to wear it over your top to make it easily accessible; pick one that's a good size for your hand, so dripping your fingers for a little chalk will not be too time consuming (do not underestimate the extra 2 seconds you can loose while reaching for chalk)
Comfort is key, but preference varies. What is the most important is that your flexibility is not limited by the clothes you wear, that they are well suited for climbing. You would not want to fall down just because you have the wrong outfit. Stay aware and climb hard!