It depends on which country you are in and what platform you are using I suppose. If it's in the US then Braintree is a good and easy to setup payment system. I

It depends on which country you are in and what platform you are using I suppose. If it's in the US then Braintree is a good and easy to setup payment system. I haven't personally used it but have heard about their ease of setup. Of course, you could use paypal if you are elsewhere but you might have to spend some effort setting it up.