I know no three-sided Greek battles but a possible setting could be squeezed into the Sicilian Expedition during the Peloponnesian War. Also there we have no really three opposing sides but you could involve Syracusans, Spartans and Athens. While Athens is going to attack Syracusans defending their outposts and the other Athenian wing they're being attacked by landing Spartans. Of course much of other battles of Peloponnesian war would work offering lots of options and including many of the different Greek city states.
If you like having your Greeks a bit later and involving Macedonians Looking so we have the battle of Chaeronea involving Macedonians at the one side and Athen allied with Boeotia. Both allieas were operating quite independently.