In my previous campaign as the Julii,my best army is:
General unit
4 archer aux
12 Urban Cohort
3 Praetorian Cavalry
In siege,pick out cavalry and add heavy onager.
In my current campaign as the Carthage,my best choice is:
General unit
3 Sacred cavalry
3 Sacred infantry
13 Armoured elephant
In siege,pick out elephant for onager.