There are two different sorts of pedals that are called "loop".
One kind acts like a mini multitrack recorder, allowing you to record a short track, and then play over it (often recording multiple passes and parts). This is a "looper", and typically will cost you $200 - some more, some a bit less.
The other type switches between "loops" that is, circuits, so that you can have different combinations of effects in your signal chain. These are generally less expensive.
If you can clarify which you want, people will be able to help you with suggestions.