Honestly while I still love the originals, the Pixel Remasters are the only way to go these days. They’re just great. Faithful to the originals with enough polish and QoL updates to make them enjoyable.
I’d recommend to play FF2 next. It introduces character development! :)
FF3 is… okay. It introduces the character class system, which you’ll see again in FF5, which is also okay.
FF4 and FF6 are the definitive pre-3d era Final Fantasy games, and should be on your must-play list.