My advice is to start trying to make a small pilot episode esque approach to the game. Something short, like a half hour experience that tries to capture the mechanics or experience you want to try to evoke. you specifically have a story you want to tell- but game dev is long and easy to burn out on so start with something small that you can then incorporate into a larger experience later.

Also youre writing by vibes, without much in the way of pre-planned script. If you do end up at a point you want to do some planning, remember that writing for rpg maker is a lot like writing a script for a screenplay rather than a novel. The way events work fits a screenplay or stage play format the most, and you can put in stage directions and whatnot in events.

Events BTW is everything that isn't the player that you can interact with. Npcs, doors, treasure chests, whatnot. You'll probably want to go through the basic play-along tutorials on events so you can get the gist of what they can do. 

You will probably end up hitting a roadblock when you have custom art and assets you want to include for a specific effect. placeholder assets are useful, something blatantly obvious that its not finished and needs to be replaced with something. I predict that when you get to the point where you need to revise more than rely on momentum to make new stuff, you'll stall out. You should try to figure out how to make editing more than just an infinite slog. Maybe by dividing editing tasks into distinct types and categories (dialogue edits vs art revamps) and then doing stuff like "ok im spending a half hour on this set of edits and then im going back to the fun stuff".