By the time of Julius Caesar genociding a few gauls left and right (as you do) as he partied around the french countryside, the romans had reformed from the old system of warfare that relied on riches and age over to the marian reforms that made the legions standardized. It became a full time occupation to be a proffessional soldier and the equipment was supplied by the army itself / state. Ironically enough, looking at the history following Julius Caesars gallic conquests these legionaires were just as likely to fight eachother under different generals (such as Pompey and Marc Anthony) as against outside forces.

art by sirspacedragurn