You should get a free hunter right away and another free one for finishing the 4 or less unit Monster Hunter dungeon, as far as I know? I got both and never had to buy or pay for anything.
And yeah, I was leaning Narga on female hunter, though I really like Kirin on her too-- it's just that it's completely useless for me because I will never have a full Monster Hunter team.
You can break down all three of each unit's evos, on a leadership basis at least as "only good with a full team of MH units", "only good in multiplayer", or "huge burst but limited usefulness".
So mostly, they're subs or inherit fodder, the more I think about them. I'm probably going to go Narga on female as she seems like the one most useful for my teams, and Mizutsune on male because that art is just gorgeous and... that's about it, really.