While I agree that Hammers, Frogspawn, Octospawn, Frammers, etc, have great movement in a tank, I disagree that they're beginner corals. They're pretty delicate and susceptible to quite a few things...
The problem with beginner corals that have movement are their growth rate, they can explode and take over a tank quickly (Xenia, Anthelia, GSP, Leathers, etc). And your tank is too young for a Nem which would also add some nice movement...
The Duncan will have some movement to it, so if I was you I would maybe just stick with that for now and wait till you're a bit more experienced before delving into some of the more advanced corals. Unless you're willing to keep a close eye on and trim back the GSP, then that's about the only one I'd recommend out of the above...