I just started Eureka.

[Naria]

I'm level 37 and it hasn't happened yet, so . . . I'm still in trying to finish the pagos stage of my weapon as there is little point of going on to Pyros until then. Most opinions I've seen say that Pyros (35+) is better than Anemos and Pagos but I've know those who disagree. If you don't like old-school style MMO grinds, or at least can't stick them out, I'd recommend doing some other content than Eureka. If you only want the AF you don't have to do any Eureka past Anemos. Definitely get on the NM train in Anemos as soon as possible; doing your challenge log for this week should get you high enough to start.