formations?

[Centurio Nixalsverdrus]

I seldomly saw that and fought the Seleukids for the last 52 years...

Well, give them time. Don't select all your troops and just tell them "run and attack". Put your troops into formation and then advance. In a suitable distance to the enemy, tell them to hold, regain formation as the line will be a bit split up due to the marching, and let your archers fire at the enemy. Once the ammo is gone, advance further, hold again, regain formation, let them throw their javelins, and then attack. Or see what the enemy does. Normally at some point they will have found their formation. If you use a phalanx too, don't click attack on the enemy, but just ram them. That should work perfectly.