I faught a series of battles against the Aedui circa 240 bce. I won Mediolanum, Segesta, and had to defend Massilia against them until finally, after 5 years of war they accepted peace, and to this day, 184 bce, there have been peace.

The trick, two legions commanded by your most able commanders. The legions, 5 maniples of Hastati, 5 maniples of Principes, 3 of Triari, 3 or 4 Velies deployed between the maniples of Hastati, one Accensi. The two empty slots should be filled with cavalry, number one choise, Extraordinari. if not available take characters, the Consular cavalry are good. Do not worry about the naked fanatics, use your cavalry as a hammer , and keep the Triari as a reserve, and deploy them to critical spots in your battle line.

Cheers.