To reach Rank 2 you need to get to Level 5. It needs exactly 15'000 XP to get to Level 5. It is possible to gain an average of about 3000 to 6000 XP during a campaign mission on the normal difficulty. So you will get this achievement in no time while playing through the campaign or after your first few online matches. When you're playing Brink for the first time you will also have the possibility to watch a video at the beginning of the game. This video explains the key elements of the game and also credits you with your first 1000 XP after watching it.