One of the critical factors in Rome's repeated successes was its logistics, giving it the ability to project power and maintain it at a distance. The Romans would build a line of fortified camps as they went, clear a road, build bridges and docks, and supply their army hundreds of miles from the nearest permanent Roman settlement. The Romans could simply park their armies on any important spot, and the Gauls or other enemies would be hard-pressed to remove them. The Romans were often able to choose the time, if not always the place, of the engagement, since attacking them in their fortified camps would be a costly affair. Since their adversaries were usually poorly supplied, Rome only had to wait until the opposition began to desert or break up to head back to their respective home territories, then take on the remaining or scattered forces, rather than fight all of them at once.
During the Republic period, Roman equipment was likely on par with their opponents overall, but more uniform, since the state began to provide at least minimal equipment for those who couldn't afford their own. That became increasingly uniform and state-provided as time went on, and the percentage of wealthy land-owners in the army declined.