I purchsed the Maigc Booster...
If you were logged in when you applied the code, first thing you do is log out and back in.
If that doesn't work, wait an hour. Sometimes, it can take a little while for the billing server to update with the game servers. After the hour, log out and back in.
If it's still not there, a bug may have occurred. It's not unheard of. Send a /petition in-game, and stay online to talk with the GM. If you have to log out, it can still be fixed, but I had a recent issue that had to be resolved via e-mail, and it took almost a week, where it would have taken minutes had I been able to stay on to talk to the GM.
@Roderick
and activated it for my account but the new costume sets do not appear in my list. What do I do at this point?