Level 47

Total Experience Required 507,990 [confirmed]

Level 100 progress: 7.44%

This is roughly:
Killing 1,694 people in Warzone, or...
Killing 1,728 people in Execution, or...
Killing 1,435 people in Wingman, or...
Scoring 362,850 points in Guardian, or...
Scoring 1,104,327 points in Annex, or...
Scoring 668,408 points in Submission.

Horde (TU4)

Completing 2,540 waves on Casual, or...
Completing 1,694 waves on Normal, or...
Completing 1,270 waves on Hardcore, or...
Completing 1,016 waves on Insane.

Or a combination of the above. Have fun!