I noticed that rome triggers marius too unless u play very hard campaign.
Also Rome seems to get a portion of every "enslave populaton", wich makes rome the most growing city even with negative 5% growth.
I had marius in 251 once wich was pre princps for me wich was kinda silly...

If u play julii hastati are all u need + equites +archers
easy to retrain in the low pop towns in gaul