This is my military center (Italy) configuration:

Rome (Capital):
(1) City (lv 3/4)
(2) Basilica Exercitoria (Lv 4 Training Center)
(3) Circus Maximus (I find the sword wielding gladiators to be an able shock troop, due to their ungodly high attack rating) xD
(4) Temple of Mars (lv 4)
(5) Armidoctor (Lv 4 Training Center)
(6) ??? -> I really don't know what put in this slot! xD

Neopolis:
(1) Town (lv 2)
(2) Trading Port (I should have built a military port here instead, but even still, the early income from this port was helpful)
(3) Cohort Barracks (will upgrade to Legion Barracks)
(4) Temple of Mars (lv 3)

Ariminium:
(1) Town (lv 2)
(2) Docks (lv 3) or Portus Classis
(3) Fabrica (lv 3)
(4) Auxiliary Garrison (Socii Equites Extraordinarii, Auxilary Cavalry and battalions of war dogs) xD

Velathri:
(1) Town (lv 2)
(2) Armourer (lv 3)
(3) Temple of Mars (lv 3)
(4) Siege Engineer's Workshop (lv 3)


That's how I did mine. Feel free to critique and/or share your own builds.