Roma Army

Legio XV

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40

Standard Legion
Praetorians are more of a flavour (tent guard) and reserve if the battle goes to shit.
Legionary cav is the legions attached very own cav unit.
Ballista can be exchanged for archers/skirmishers, but i personally like my armies with a bit of siege capabilities.
In battle place eagle and evocati cohorts in the first row, aided by two legionary cohorts, with eagle cohort on the right of your army. Second row of legionary cohort. Praetorians in reserve and auxiliary infantry on flanks. If outnumbered use simple axis (all infantry in one line). If enemy has many skirmishers running charge (look it up on google).
My favourite tactic to use with this army is to place eagle and evocati in one row behind each other on the right with the legionary cohorts placed in two rows to the left of this strong right wing. Punch through the enemies left then roll him up while holding the front with your normal legionaries.