Level 14

Total Experience Required 24,425 [confirmed]

Level 100 progress: 0.36%

This is roughly:
Killing 82 people in Warzone, or...
Killing 84 people in Execution, or...
Killing 69 people in Wingman, or...
Scoring 17,447 points in Guardian, or...
Scoring 53,098 points in Annex, or...
Scoring 32,139 points in Submission.

Horde (TU4)

Completing 123 waves on Casual, or...
Completing 82 waves on Normal, or...
Completing 62 waves on Hardcore, or...
Completing 49 waves on Insane.

Or a combination of the above. Have fun!