Anywhere you think you see something interesting. There is no need to play them in order at all as the stories are all self contained. The names I tend to see most often are FF6, FF7, and FF10 (11 and 14 are MMO - what I actually started with).

Additionally, the beauty of final fantasy’s idea of having recurring names/enemies/etc is that even if you play a newer game before an older one and see a name or thing you recognize, you will always come to appreciate the callback even if you found out about them out of order.

Just keep in mind that since these games have spanned decades, the style and complexity of game will obviously have changed greatly, I know I personally have a hard time playing through really old games so it would be harder for me to start and get hooked by playing the older games