Who mentioned IX?
Oops XC I must have been very tired. Just ignore me XD.
XI looks like the most popular starting point here.
FYI XI is an MMORPG from 2002, so I don't know how active its community is today.
Just saying, I really don't like games that haven't aged well. They become cumbersome for me to continue and I usually end up dropping the game.
FFI, II and III are the ones I would say have aged the worst.
IV is where the story telling really started to take off, and has,
arguably, gotten better with each entry. So if you prefer story-driven games, any game in the series from IV and after would work.
If you prefer photo-realistic graphics, VIII is where character models, both in and out of battle, would begin to have realistic proportions.
Gameplay is something that changes in every game of the series, so it is difficult to suggest a good game, without having to detail the differences between the games, but if I should rank the gameplay from hardest to easiest it would IMO be like:
VIII < I < III < II < XI < XIII < XIV < XII < V < IV < X < IX < VII < VI
Like I said previously, you should check out a few of the games on Youtube to see which ones seem the most to your liking.
Alternatively, FFXV is releasing in September, so you could get that for when you get yourself a PS4.