Best Factions to play as for a beginner.

[Kamakazi]

I had an absolute blast with Parthia. Their play style is much like the Nomad Factions in that you (well at least I) use fix and fudge (for lack of a better word ;) ) tactics.

Use a small infantry core to fix the opponents and then destroy them with shock cav and horse archers. It is literally the easiest tactic ever. Horse archers require micro though so as a warning don't approach this unless you have some dexterity.

Placement lets you go south and southeast to take out Selucid and all its little baby puppets which I found way to easy.