Limited Run Trophy
Complete Level 12Story-related and cannot be missed.
To level up you must complete Campaign Missions, as they're the only source of XP so just keep completing Campaign Missions until you reach Level 12 and the trophy will pop. As you continue to do missions, more Campaign Missions appear on the map. You can do these in any order you please and you'll always gain XP no matter which one you do.
See Roll Credits for more information and tips.