I always use the manipular formation. The exact ratio of units that I use are not completely accurate. I use 5 hastati, 5 principes, 3 Trarii, 2 velites, 1 general, one equites, one italic cavalry, and 2 itallic infantry. The Hastati, Principes, and Triarii are in three lines, and I place the Itallic infantry and the flanks behind the Principes. The Cavalry remains in the rear or out on the flanks.