OT
Prequel Trilogy
Sequel trilogy

OT is fundamental, prequel is supplemental and sequel is live action Expanded Universe.

The only one in my mind that is essential is the OT. I don’t love the sequel but force awakens if goofy fun in places, and i like aspects and not the whole of the last jedi. Rise of Skywalker is an acquired taste and i’ve seen it a few times on cable tv, i mean its watchable. Its a better experience with the novelization and Shadow of the Sith, but supplemental material shouldn’t be necessary.

I’m rating them as whole trilogies as stand alone films Empire would always come out on top. And Last Jedi is easily the best of the sequel movies. The prequel is tough i have real nostalgia and love for the good parts on Phantom Menace and its being the closest to Return of the Jedi in quality. I’d have to pick that as my favorite but Sith is always going to be the top rated just for the last third of the film. Attack of the Clones was the worst in the Saga until Rise of Skywalker. I’d personally probably still rate it dead last.