Sorry about the delay. Went to bed, got up, went out, came home, now on reddit again. Anyways:

This doesn't seem to have been true among the Gauls

Sounds interesting. Pretty much every sedentary pre-modern society I've studied had organised their military around the 'professional warrior bands supported by non-professionals called up for a campaign' concept I outlined in the last post (most of the exceptions were those with standing professional i.e Imperial Rome and China). This inevitably led to a disparity in training between guys whose profession was war and who spent all of their time practicing small-unit tactics with other professionals in their lords household and guys who had regular employment as farmers, artisans etc. and who might be called up to fight alongside a bunch of other guys who they had never fought with or even met before. There was also usually a noticeable difference in equipment between elite forces whose equipment would likely be provided by their lord and non-professionals who would have much more basic armaments, this was usually manifested in body armour (although as you pointed out, I did neglect to mention helmets in my last post which were a pretty big deal, especially for guys who were more lightly armed and thus dependent on them for protection). The Gauls were of course famous metal workers but this would be more an issue of military logistics and bureaucratic infrastructure than anything else.

Gallic cities sound like an interesting topic. From what I understand Romans and Greeks considered most other civilizations 'barbarians' mostly due to their lack of cities to I'd be interested to learn more about urbanization in Gaul. Also I'm more than a bit leery of 80,000 warriors being sustained in a city for any extended period of time. I honestly can't think of any other occasion when that many fighting men were kept inside a city like that, even in much more urbanized societies. Good point about Gallic agriculture though.