Instead of saying level 1, level 2 Knights etc, which would sound a little mathematical, one can abbreviate levels to adjectives instead, making your imagination run wild. Take the numbers away and say that all level 1-3 are conscripts/green, 4 to 6 are trained and so on.
Green/Conscript
Trained
Regular
Veteran
Expert
Crack
Elite
Legendary
For instance: Elite Palace Guards, Legendary Rainbow Archers, Crack Sharpspeer Halberdiers, Veteran Noble Knights.
