I started creating a fantasy world, but I don't know how to start layering the story? Start with the global history and then build up from it the history of the races, the nations and so on, or should I start from the history of one character and then build it from bottom?
I think it would be easier to create a world around a character than a character within a world. For me, ideas start off of an idea about a character to create a story around. So the character would be the spark that puts everything else in place. So I would start with getting the main character(s) bio built up first. In the bio, are they the descendant of a ruler? Are they from a family with deep roots? What kind of job do they have? Do they have any titles? skills? where do they live? Do they have friends? Family? are they a wanderer or pledge allegiance to a nation? As you start answering these questions, the general picture of the world can be more easily filled in. The history would be practically written itself as you just take the character's bio and start using the general information to build the world history based on that information.
This is how I would approach the topic. I am sure others prefer to build a world first and then create a character to fit the world. Either way, you honestly really can't go wrong, just depends on your thinking process and what starting point is easier for you.