Just travel 50,000 steps with the main character you are navigating with.
I just obtained this achievement when I hit the Rainy Giza Plains on my way to the Ozmone Plane. This will come naturally as your making your way through the world of Ivalice and should not be hard at all. This is pretty much an Unmissable achievement unless you quit playing the game after 5 hours. It will come in due time.
EDIT: Negative vote for giving a solution? Wow. Tough crowd. :/