1, 4, 5, 6, 7, 8, 9 and Mystic Quest are good. FF10 has Blitzball which makes it worth playing and FF10-2 has a decent quest system and amazing combat system which makes it worth playing. FF2 isn't for noobs, so don't play it. FF3, 11, 12, and 13 are the worst in the series so don't bother. FF12 has a lot of good qualities, likable characters, well developed towns and landscapes, a great quest system, amazing graphics for a PS2 game, but the combat kills the game, and it's not tjust not controlling your characters, the combat is boring as hell.
I'd say start with Mystic Quest. First off, it's a beginner RPG, but it's got a lot of good qualties to it that make it fun. You can switch your weapons at any time. Some enemies are weak against axes, some enemies are weak against bombs, other enemies are weak against claws, others are weak against certain spells. You use the weapons to progress through the game as well, using a sword to push a switch, axe to cut through trees, bombs to blow stuff up, or the claws to climb . It's a pretty good looking game graphically, it's got fairly good music, and a decent story.
