Level 23

Total Experience Required 68,021 [confirmed]

Level 100 progress: 1%

This is roughly:
Killing 227 people in Warzone, or...
Killing 232 people in Execution, or...
Killing 193 people in Wingman, or...
Scoring 48,587 points in Guardian, or...
Scoring 147,872 points in Annex, or...
Scoring 89,502 points in Submission.

Horde (TU4)

Completing 341 waves on Casual, or...
Completing 227 waves on Normal, or...
Completing 171 waves on Hardcore, or...
Completing 137 waves on Insane.

Or a combination of the above. Have fun!