I world-build for fun, and there are a couple of ways I do it, depending on how I want the world to be. Sometimes, I leave things ambiguous, but what I do most of the time is as follows. I mostly do fantasy, FYI.
First, decide the top-most of the deity/divinity pyramid. Then, I assigned each of the aspects of life, what people would actually care for, to each, or a group of deities, and had them be the representation of such. They are my primordial, the ancient, the lost gods so to speak. Most of them, in my worlds, tend to be forgotten, hidden, or slumbered, except a few. Then I have the ancient, Old Gods, lording over major aspects of life and nature, or what the people would consider important. Then, there are the New Gods, which are the gods of things that mainly pervade civilization things and such, or gave Old Gods new domains to lord over, or make them a patron god of something. Some domains are shared, some don't even though they should, and sometimes, they could make nonsense.
Sometimes too, I will give the people of the world mythos and stories that might differ, twisted, or inaccurate to the actual creation myth, depending on if the gods in a given world are real or not, to how involved they are in mortal affairs and such. Here are some examples, but they are not fixed in all my world
Ancient Gods: Death, Light, Night, Day
Old Gods: Ocean, Earth, Wild Fire, South Wind
New Gods: Wisdom that includes Writing and Learning, Ocean will include things such as sailing and fishing, god of smithing might not be the god of fire but may be related or connected somehow.
Sometimes, I will only have a dozen plus gods, but there is one world where I have about fifty-something gods and deities, with a dozen major gods, which can consist of all three categories I have above pertaining to the belief of the people, as the main point. Not all gods are worshiped, and it depends on the geographic location, professions, and culture. Most cities will have a couple of temples/shrines that worship some or most of the major gods and half a dozen of the minor ones.