A couple of codes that you can use:
YAX4AS6X (unused)
GRFWWFJM (unused)
H9PAXDKX (unused)

Using a code will give you bonus items to get you started, including:
Friendship Circlet - a 20% exp boost while under level 25
Aetheryte Tickets x99 - Free teleports through Eorza
Silver Chocobo Feathers x10 - Trade them in for special items
Fistbump emote!