Afford to be in? He, might as well go all the way with this.
Well, for Rome, probably the whole Hastati, Principes, Triarii thingy, I think I´d be counted wealthy enough for that. As for Greeks, maybe a normal Hoplitai, after all, they are drawn from well to-do citizens.
As for the Seleukids, I´d probably be (counting that I´m of Hellenic descendancy) an Pezhetairos, bordering on Prodromos, seeing as how many nobles there were of that kind.
For Ptolemais, the same as the Sele´s, though maybe I´d be an Galatikoi Kleruchoi.
As Makedonia, probably just a Hoplitai or Pezhetairoi, nothing exciting.
For Luso, either Gestikapoinann or Scortamareva.
For Getai, either Tarabostes or Komatai Thorakitai Stratiotai.
For Sab´yn, probably Abbir Ezra'him.
For Pahlava, maybe Dehbed Asavara.
For Pontos, either the normal Hoplitai, the Lonchophoroi Hippeis or If I´m really cool, the Galatikoi Kuarothoroi.
For Sweboz, most likely Herunautoz.
For Sauromatae, I guess I´m bordering on one of the many Noble HA´s.
Same goes for Saka-Rauka, but in Indo-Saka days maybe I´d be an Hoplitai Hellenikon.
As Karthadastim I´d likely be a member of the Carthaginian Citizen Cavalry, as long as I was a Carthaginian citizen, were I Libyan or something else, that would change of course.
As Hayasdan, maybe the Mardig Sooseramartik.
As Epeiros, Hoplitai or Pez.
As Casse, maybe the Botroas.
As Baktria, the Pez or Hoplitai Indohellenikoi seems likely.
And as Aedui and Arverni, the Bataroas.