The Atelier games are in stand alone arcs. I would suggest to start with the Ryza arc. The first one is called "Atelier Ryza: Ever Darkness & the Secret Hideout". Not only is it on of the newer games with tons of modern conveniences but it also has the best main character of them all (fight me, I said it). The DX versions came out last year which are updated versions with additional content (similar to how Atlus double dips). Not a fan of this practice but if you're getting a version now this is the one to get.