I read the first book in The Long Earth series by Terry Pratchett and Stephen Baxter. (It was really crappy and saw no point in continuing the series.)
The key “magic” in the book is a device for teleportaion between parallel Earths. Want to rob a bank? Jump to a parallel Earh, walk to where a bank vault is on the original Earth. Teleport back, grab what you can, teleport to the other Earth. Riches ensue.
Or they would except various things are introduced either by the magical intrinsic nature of the device or by people taking precautions. E.g., you can’t carry iron (but blood is okay). So your sort of have to start an Iron Age from scratch on the other Earths.
Yeah, it’s very gimmicky for the Purpose of Story. Etc. But something the OP should check out for not duplicating ideas and such.