What type of binding do you want?
This is probably the first thing you need to think about. Not every type of binding requires a machine. For example, slide binders and binding screws can be done by hand, but for pretty much every other type, you’ll need a binding machine.
If you’re using wire or comb binders then there are various machines you can choose from depending on how much material you want bound and how much you want to spend.
If you want thermal binding, then you have no choice but to use a machine as the material is bound using heat. There are different thermal binding machines available, some of which allow you to bind several documents at once.