I actually have no idea. But, I started with character first. The world came later, as a way of shaping the people (and monsters) I wanted to follow.
Some of this even depends on what you are crafting. A technical science fiction story is probably going to go smoother if you world-build for awhile first, and same thing with the most complicated works of fantasy. Modern fiction, stuff set for the most part in our world with at most one or two things off kilter, you probably want solid players before moving too far out. Unless the off-kilter thing is what sets everything into motion.
It really doesn't matter, so long as you pick the one you are most drawn to (the thing gearing you toward writing the damn story) and you can piece the rest around the most solid thing you have. You also won't make yourself miserable by doing one you weren't as fluent in right out of the gate-you get frustrated enough with that, and you might not pick up the pen. And that's hazardous to your writing health.
|"The Study"-a 3D modeled room created as a werewolf history archive.|
My novels are a trilogy, the first being the closest to modern, when the virus arrives. The second deals with a bit more tech, a bit more politics, as it's further into the recovery after the havoc of the sentient sickness. The third, well, guess where that is going...Back to the past, a bit more old world, where I can show the story of Taisho's ancestry, of her parents, and of what the world looked like when humans discovered werewolves had been walking alongside them for centuries.
All of this actually started from an idea for a single character, Taisho's mother. Yeah, I know, right? That was a far mark from what I made. But it was that character from which I put the world together. I'm not as good at world-building as I am at people-building, but I'm good enough at it to be able to fill in the blanks a personality leaves open. And that's just what you have to do-be good enough at the one of these two things you like doing the least.
You might even be that rare breed of human that doesn't need to outline plot points, worlds, or the people that exist in them before you have a story. But then, what the crap are you doing here?