Great to see a decent replay database im happy to share some of mine. mostly all flatland.
My plan with the barbs is to entice the roman player who has the advantage to send his cavalry ahead of his infantry and weaken his cav so as later in the game his oppurtunity to flank me is drastically reduced and i can gain a numerical advantage. I do this my making my archers look vulnerable and using them to target his cav promting them to charge me ahead of time. I also with spain use good light infantry to counter charge the cav when they commit to attacking my ranged units.
To soundly defeat a roman player with the gauls on a flatland map is not an easy affair ive never seen it done but i got a plan and though tricky it works if im on form.
Cartrage is a more basic affair and im new with them using a reliable sword and shield style approach refusing my flanks and using a pinning motion combined with brute force i could use some advice for refinement and i developed this strat to combat the defensive onanger archer style players.