Level 13

Total Experience Required 21,347 [confirmed]

Level 100 progress: 0.31%

This is roughly:
Killing 72 people in Warzone, or...
Killing 73 people in Execution, or...
Killing 61 people in Wingman, or...
Scoring 15,248 points in Guardian, or...
Scoring 46,407 points in Annex, or...
Scoring 28,089 points in Submission.

Horde (TU4)

Completing 107 waves on Casual, or...
Completing 72 waves on Normal, or...
Completing 54 waves on Hardcore, or...
Completing 43 waves on Insane.

Or a combination of the above. Have fun!