I'd recommend coming up with an entire story, learning RPG Maker, finding tilesets that fit, making your own sprites for the things you can't find good tilesets for, building the maps, programming the interactions for every single interactable piece, learning Daz3D, scouring the internet for every single costume/pose/body type/environment/lighting rig/piece of genitalia you want, making the little avatar images for dialogue, WRITE all the dialogue, spend hundreds of hours making the images perfect, doing half of these these two or three times each because of branching scenes that play out differently, spending untold hours play testing the whole thing over and over again, inevitably go back to fix things that you find out are broken while testing and re-writing dialogue that needs work, testing it all over again, and doing that even a fraction as well as PG is doing it and you may gain an appreciation for the time spent here.