Each binding manufacturer has a range of models and prices. As with skis, a binding should be selected based on the way you ski and how much you weigh. Unless you are an aggressive skier who skis the steeps, the bumps or races, you should not buy a high-end racing binding. The middle or low-end models may be suitable for you. Ask the salesperson what binding is best for you.
All ski areas require that skis have ski brakes.
Ski brakes are a spring-loaded pair of arms that drop down and grip the snow when you release from your bindings. They prevent the skis from running away down the slope, endangering other skiers. You should buy bindings at a shop that has a certified mounting service. Most important is the pole length. Any easy way to determine what length to buy is to hold the pole upside down and grip the tip above the basket.