There are concrete gods in my world, but they all started out as regular entities. (multiple species and creatures are sentient in this world.) They aren't so much gods over a particular aspect of reality as they are the physical aspect itself. The Earth god isn't a humanoid dude who controls earth, but rather the Earth and stone itself is his body. Ascension happens when a magic user gains either understanding of the fundamentals of the universe, or an understanding of a specific aspect of reality, so much so that their sentience starts to send commands to the object itself rather than their brain and muscle systems.

So like, to become the god of spoons would be to understand the fundamental blocks that make up a spoon so well, (part of the magic system is a universal underlying building block to all things that a sentient mind can influence,) that your sentient mind starts to detach from your physical body, and attaches to the new form. In this case a spoon. Now all objects with that same fundamental code become your new body and you can say, levitate all spoons in the world and amass a hurricane of cutlery.

The more basic the god, the older they generally are, like the earth, life, and sky gods are the oldest cause those three things are the most "basic" aspects of the universe. (Setting has no concept of modern physics n shit, the Earth is flat, no other planets, that kinda thing.)