The Marvel cinematic universe is a complex beast, and growing ever more complex by the movie. Take your typical world of earth, toss in some superheroes and supervillians, and then go to town on it. Add cities that don’t exist, a futuristic country in Africa hidden from the world, other dimensions where near-literal gods dwell, and alien planets gallor. It’s a thick layer cake of shared universe where each layer has been built one production at a time until over a decade later we have a complex and vibrant universe that is far more complicated than “modern Earth” could be.
Now, go build your own fantasy world with that level of complexity, and do it in a single book. I’ll wait. Tick tock, times a wasting.
Not easy, right? There are a ton of variables to think about, everything from the name of the world itself to the types of shoes worn by a particular sub-culture on one of the numerous islands that form an archipelego between two main continents in the southern sea north of the polar region, although in this case the planet’s magnetic field is at the equator and each side faces half a planetary year in darkness because of the way it spins, and this is a very long sentence that needs to eventually end.
Worldbuilding is a big deal, especially (and mostly) in fantasy and science fiction. There are whole internet forums to talk about it, and classes you can go to learn more about it. And it’s great stuff, but you can get buried in your details and forget the whole purpose of your story. The idea with worldbuilding is to show just enough in the story to root your readers heavily in a moment and place without overwhelming them with a great deal of telling (though as always, there are exceptions to every rule, and sometimes you do need lots of telling to get something important across). I think it’s best to leave the reader with the impression that, while they’ve barely had a chance to scratch the surface of this world, there’s an infinite amount of stuff to discover if only they could pull back the curtains further. That bodes well for you, the writer, too, because it helps create anticipation for more of your stories, particularly if you’re writing a series.
Personally, I do very little world building. Just enough to put the basics in place if it’s “not really Earth.” Then as I write, I let other details enter into the writing and help build that layer cake. But I know plenty of other authors who do a buttload of planning before pen ever touches paper. You’ll have to find what works best for you. The key (for me at least) is being able to use shortcuts to create a world and its myriad backstories as quickly as possible. How far do you want to go with your worldbuilding? Are you going to model an entire planetary system, with an unusual orbit and the weather patterns of your planet(s)? Or do you just want to take something earth like and modify it with different continents and a fantasy setting? Whatever the case, set your parameters and focus on what you need for the story, and how much you can get away with skipping.
I recommend you start out on Reddit. You can create an account and roam around for a bit. Once you’re settled, or assuming you’re already an old hat at Reddit, go to the wiki at the Worldbuilder’s forum. Orient yourself and check out their Reading & Resource list link. There’s a ton of great stuff in there, from map building tools to discussions of medieval economics. You’re going to find absolutely a plethora of details to lose yourself in. There are other good Reddit forums as well, such as Writing and Fantasywriters, so make sure to check out all of Reddit and see what else is of use to you.
One of the biggest tools I use for all things world building is Fantasy Name Generator. It’s not just for generating any number of fantasy name types, from elves to gnomes to lamias. There’s also generators for real names for a huge number of Earth cultures, which I use a great deal in all my stories. There are place name generators, description generators, even map and magical treasure generators. I can’t stress enough how useful I find this site, even if it’s mostly for creating names for characters. But I rely on it heavily, that’s for sure.
Don’t make world building the only writing you do. Get in, get out, get your story down and let the world support it without supplanting it. You may not be Marvel Studios, but they’ve got more than fifty years of back story to play with and we’re still creating our stuff as we go along.