As the Arverni I didn't disband a single unit, preferring instead to concentrate the troops into one fullstack and go rampaging around Gaul. When I had almost finished unifying Gaul by siege starvation (I didn't exterminate) I was in the positive. Part of the reason being that I set as high a tax rate as possible in all my cities. It took me 60 turns to crawl out of it, but it was alright in the end. Once I took Massalia and exterminated it, things turned rosy. But then, by that time I didn't have a single unit above half strength, so it was pretty touch and go.

One thing that helped me immensely was that i used my starting mnai to queue roads, a coupla lugoae to garrison my home provinces, and spent all the rest on iaosatae. I slung Gaul to its knees.