As well as getting longer spears, a unit of Macedonian pikemen gets 50% more men than a unit of hoplites. The extra men give the Macedonians a big advantage over the Greeks in phalanx clashes.

Use archers and peltasts to weaken the enemy phalanxes before your phalanxes engage them, and hit them in the flank & rear with your cavalry.

I have often found that in an open battle, the AI will break up its battle line and have individual phalanxes trying to chase down the faster moving archers and peltasts. If you keep your phalanxes together, you will be able to destroy the enemy piecemeal.