I love my Arcachon, but it's very chaotic. If I was just starting out I'd be looking at Zonasa or Cathay, as even if they get into trouble they're in no danger. All four of the Northern Realms are either taking a beating (Aenelia or Ohnar West) or in serious danger if they lose the war (Arcaea or Arcachon).
It's the mix of fire and baptism you're looking for, really, as well as what kind of character.
I like to think of the realms as quasi-historical themes:
Arcachon is Celt, the realm has very much a "horde" feel. If you liked the Urak-Hai in LotR, you'll like Arcachon.
Arcaea is Charlemange's empire, The Darker Arthurian stories fit there, as would Game of Thrones.
Ohnar West is a republic, and that's sort of their thing. Trading and Internal politics are big themes there.
Cathay is rebranding and I'm no expert, but I have it on good authority that it's a place for telling pennants and banners stories.
Aenelia south I'm not an expert on.
