Well, that's a tough call, but the earlier step workouts are easier to learn because Cathe's style used to be different; she used to spend more time on the teaching portion of the workout than she does now. I swear I do not get money for recommending this, but I think Cardio Hits is the best place you can start... or with the Basic Step/Body Fusion workout. That one REALLY breaks the steps down. After a while, it does get easier!
Good luck!
Marie