I was recently reading Nightmare's Call. If you know about it then you would you that the mc makes basically a church/cult of his own. I want to find novels where mc makes his own church/cult. Exclude Lom since I already read it and even then the church part isnt good.
Lom? King Shura. He becomes the pope of a "cult." The same for Tales of Herding Gods. The Experimental Log of the Crazy Lich. He creates a religion with his God avatar. Warlock of the Magus World. In the later chapters, he schemes to build a religion in a rival plane/world. The child of sun and moon. The MC is the son of the Sun goddess and Moon goddess, he then becomes some sort of the blessed child for the both of them when he descended to the mortal plane. It was in RRL, sadly, it got removed by the author. Just recommending this in case it gets posted again. The bible. I'm not sure if you've ever heard of it, but it's pretty popular. It's about a saint who's the son of god, and it's a collection of stories about establishing morals and stuff. Through the MC's journey, he establishes some form of a religion. I'm gonna spoil you a bit, but the MC dies.
Bible is best selling book but there is tragedy and gore and many other tags which might turn you off.... Some of its fans are a little crazy so beware...they think it's real.