Athene is really huge, and a big priority for pretty much anywhere in the game.
However, if you are concentrating on dungeons now, especially if you don't have an Anubis, Espirita appears to be a major asset there, since her spirit can hit so many targets at once, and then do it again so quickly. Quicker than Anubis. And her spirit's hits aren't bad.
So in general I'd say Athene by a mile, and don't hesitate to max her out. But if you're doing dungeons right this minute, I'm not so sure that Espirita wouldn't be better.