Level 6

Total Experience Required 6,105 [confirmed]

Level 100 progress: 0.09%

This is roughly:
Killing 21 people in Warzone, or...
Killing 21 people in Execution, or...
Killing 18 people in Wingman, or...
Scoring 4,361 points in Guardian, or...
Scoring 13,272 points in Annex, or...
Scoring 8,033 points in Submission.

Horde (TU4)

Completing 31 waves on Casual, or...
Completing 21 waves on Normal, or...
Completing 16 waves on Hardcore, or...
Completing 13 waves on Insane.

Or a combination of the above. Have fun!