Hellooo, there isn't really a play order, but generally I would recommend oldest to newest, which is listed on my front itch io page!
All MO games take place in the same universe, but they're all stand-alones!
MO Iris will be paid yes, and has a demo out, if you count that as a sneak peek! I would recommend Rieffe or Lanneis > Reqieu > Septem.
The game won't need a walkthrough, since it should be very straightforward!
From hereon, most of my games will be paid, except maybe the clown one? I hope you enjoy all of them!