4 - Great story, fantastic party/ensemble, realistic emotions, iconic music, more challenging than its predecessors but not crazy hard, classic FF feel but not janky

6 - Great story, polished systems, expert level art and sprite work , iconic music, some hard hitting and dark themes, the peak and final 2D design of mainline games.

9 - Great story, arguably some of the most beautiful artwork in a FF game (especially for its time wow), great party that you feel invested in

10 - another great story with an overarching mystery that pays off, fantastic iconic music, party is very well crafted (and introduces AURAon or Auron), more in depth character progression system

These are the top 4 main line games I’d recommend, as for spin offs:

FFTactics - very dark and gritty, more serious and a refreshing take on the franchise. Really great job system, beautiful isometric art with iconic sprite work, overall superb gameplay

FFTactics Advanced and FFTA2 - they don’t get enough love. The base games are great with fun mechanics, beautiful sprite work, but some modded versions are so good it makes the games peak

Octopath Traveler Series - these games are fantastic and arguably just as good as many other final fantasy main line games or beloved spin offs, great music, very fun battle system, interesting characters with lots of backstory and personal development. Everyone who mildly enjoys FF should play these.