Level 22

Total Experience Required 61,404 [confirmed]

Level 100 progress: 0.9%

This is roughly:
Killing 205 people in Warzone, or...
Killing 209 people in Execution, or...
Killing 174 people in Wingman, or...
Scoring 43,860 points in Guardian, or...
Scoring 133,487 points in Annex, or...
Scoring 80,795 points in Submission.

Horde (TU4)

Completing 308 waves on Casual, or...
Completing 205 waves on Normal, or...
Completing 154 waves on Hardcore, or...
Completing 123 waves on Insane.

Or a combination of the above. Have fun!