I dont' mind playing as Britannia but they are a little low on income and their position on the map with only 1 settlement in Gaul which has low population.

Plus they only get Chariots as Cavalry which are useless i think in both settlements and open land so i don't bother with them and just leave them out of the battlezone unless their Missile Chariots which i keep out of the battle but in range of their units. In settlements they can't really move.

They are an Infantry Faction i'd say because of their Druids and Woad Warriors and Chosen Swordsmen. I just conquer Gaul and Germania and ally with the Roman Julii.