I'm only playing on the default difficulty nothing hard or anything but they're so easy to train a million early on that I managed to overtake every civ that started on my continent way early without even realizing it until I finished exploring the borders, I've explored the one fairly large island nearby and gonna settle on it soon, it just has some city states that no one else has contacted, I think most are converterted barbarian tribes. I can't explore anymore until I have ocean travel and I'm on pace to get that earlier than anyone else should unless they steamrolled their tech tree on the other side of the world