Legions

[mrdun]

Basically the same as any faction, infantry with what ever is needed against your foe.

[Quirinus]

Except for Parthia, Armenia, Scythia, and, to a lesser extent, Carthage. For the former three, horse archers should be the backbone of the army instead. For Carthage, I like to have a cavalry-centric army with infantry relegated to a support role, but that's just me.