Well I can give you my understanding of it all. I believe in God, that he created all things that we know of in this physical universe, I do not believe it created itself. But " Before" God had all this created, there was what was there before in his spirit world; we don't know a lot about this spirit world. But I believe that God was alive first and at some point he gave birth to Christ ; he somehow brought Christ out of himself. And Jesus became the first born of God. I think then they created the world of angels and other spirit beings, perhaps millions of them, I don't know.
I think God was so pleased with how Jesus turned out, that made him want more children, and that desire was the beginning of them planning and creating humanity. For several reasons God wanted humanity to first be in the flesh, But God obviously wanted humans to eventually become spirit beings , but only after we experienced things that God , in his wisdom, wanted us to live through. I think sin and evil are two of those things. God had satan created to represent evil, to be the father of sin.
Like a cook preparing a dish, God wanted humanity prepared for his Kingdom, before we actually got there. Like a great potter molding clay, God is using satan, sin and evil, in our preparation for our eternal future; he wants us all to " Know good and evil." This is why satan was created, because evil had never existed before, so it is soley for our experience. For some reason I do not understand completely, it must be an experience God feels that we need.