Celts and romans are great, here are my best characters of Romans and Celts at the begin of the game:
Gordon:-darts of ice (2 targets).
-beast call (2 beasts).
-74% chance to hit with a spear.
-70% chance to hit with a sling.
Publius:-96% chance to hit with a spear.
-94% chance to hit with a javelin.
-4 at strengt (much damage)
-armor use, hardiness and shielding at 2
If you play with these characters, boths sides are fun