I'd recommend starting here, since it deals with Pontus' faction leader at the beginning of the game. From there, you can go through his various successors and try to chart their expansion. However, from my own cursory glance, it appears that Pontos did very little until the reign of Mithradates II, when it went to war with the Seleucids. If you stick to that, you could be hanging around Amasia for quite a long time.

Cheers.