Carbs and fats. Unless you're tearing down muscle via weight training or high intensity sports, you wont' need a bunch of extra protein. Carbs are your body's preferred source of energy. Protein alone won't provide the calories you need to maintain normal weight. That's bad advice. Carbs are much better for keep your body sugar up and are protein sparing / muscle sparing. If you force your body to burn protein for fuel, you'll compromise your lean muscle mass along the way, and create metabolic lag. Eat the carbs, any you body will burn that, instead, and spare your muscle, as well as have a higher level of performance. Glucose is the name of the game. Fats are also good for long term energy and unless you have very high blood sugar / high insulin when eating them won't make you fat, if you're eating the good ones (poly and mono). If you're dancing for long periods, what you need is fat.
EAT. Lift weights. Simple stuff for a very basic question.
If you eat more calories than you burn you'll gain weight and vice versa. It's not at all complicated, and very much a common sense thing.