You can't ski without bindings. To a certain extent bindings are bindings and although there are some performance differences between them the biggest change is the materials. Cheaper bindings tend to be made with lots of plastic, where as more expensive ones have more metal in their construction. More metal makes the binding stronger, more durable and will last longer. If you change your ski's in the future you can then transfer you bindings to them.
When selecting a binding choose a binding with a brake that is min 5mm wider than the waist of the ski.