Something like the Jedi faith or something more nefarious like Scientology which exists to make money off its believers? Because if the latter, you're gonna need to fuse it with other shit (like LRH's Dianetics) to get a following--just like you don't tell everyone who gets into Scientology about Xenu (not at first), you wouldn't be telling just anyone who gets into this faith about Cthulhu/a knockoff of it.