Playing as Gauls, How to Avoid the Early Roman Juggernaut?

[A Terribly Harmful Name]

I'll try forts then, that's quite a cunning idea!

[Philippus Flavius Homovallumus]

I've had good experiences with forts playing as Macedonia, I achieved about 100 years of peace and Alliance with Dacia by building a hard frontier with forts in all the passes and at all the river crossings, I also maintained large garrisons and I had a roving army od scythians with an FM up there killing bandits and rebels.

The AI is not quite as stupid as it appears, if you make it hard enough for them to attack you they won't bother half the time.