Whom should I play as next?

[zooeyglass]

No Phalava choice? Boo! You can stay nomad or go go Parthian, plus they have better units/recruitment/economy/position/etc than Hayasdan, especially once you start up with the reformed gov'td. And they get an Early and Late FM. Otherwise I'd play Getai and be original and storm the Baltics and Russia. Let those overbearing Greeks slaughter each other for all you care.

i was tempted by pahlava, but my last campaign (prior to the casse one) was baktria, so i felt a break from that side of the map would be good, hence the rather central choices.

they may well be the next one. although a northwards getic expansion, or a hayasdan campaign, are both strong contenders.