I prefer the Aedui, mainly because they to me seem more flexible in the begging, if you are careful you can in the first few turns draw the entire Averni army in Vienoss and Gerovia in carrion feed by simply looring them into the fords and woods. Next I go after the last Averni holding over by Germany wait for them to sally, crush them and then return your army to Bibracte for retraining. The next step is to squash the Sweboz quickly, so all you need to do (since in the beginning the Sweboz have allot of stick and club wielding militia) is get one huge stack of troops with allot of swordsmen and the march them off to Germany as quickly as possible and start taking out Sweboz armies as soon as you see them and take all of their town to nock them out of the game, and leave say on unit of levies in every town and set up client kingdoms. The only major complication is the fact that there will be allot of Sweboz hiding in the woods who will attack the cities you have freshly taken causing you to have to send the army back to get them. And while you do all of this do remember to get an Oppida and lots of troops for Mediolanaum so the Romans can't take it.