Walk through the gate (there's nothing to collect this time) and come out the other side. You'll come upon the man that was blocking the gate before--the same man who was standing in the Gym when you battled Roxie.
Before long, he'll notice you and drag you all around Pokestar Studios, forcing you to watch a movie and even create your own before finally allowing you to go off on your own once more.
To create the movie, simply talk to the blonde-haired man next to the door at the back. Select whichever option you like and you'll then be taken into the studio. Here you will have a fake Pokemon battle. Once it's over, whether you win or lose, you're free to explore.
If you want, you can play around with Pokestar Studios and film your own movies. It's not necessary to complete the game, but makes for a fun distraction when you're tired from battling. Anyway, when you've had your fun, head back to Virbank City to continue your Poke-adventure.