I've played 7-9 12, and 13 to various degrees of completion. In the end, it really depends on what you're looking for, and what you're willing to put up with.
The games aren't strictly turn-based, but it can seem that way in standard encounters. If you're trying to avoid turn-based, 12 and 13 are your best bets, though I'd avoid those. 13 is repetitive in gameplay and confusing in story, and fells way too long. 12 is solid, but it's easy to get bogged down in the story and mechanics.
If you're willing to put up with not-quite-turn-based combat, there's 7,8 and 9.
9 has the best story and characters by far, but the game mechanics bog it down. It's really slow, especially to start, and it takes a long time to pick up speed.
8 is a mess. It's slow, boring, counter-intuitive, and has a really weak story, with the exception of a somewhat interesting but pretty shallow love story.
7 is a good all-arounder, and a good one to start with. The mechanics are simple, but have depth, and the story is good, though a bit silly. It's pacing is also pretty good, with the exception of a notoriously long-winded flashback about 6 hours in. The graphics are also very primitive, especially in comparison to other games in the series.
So if the battle system in the earlier titles is an issue, try 12, though beware its complexity. If you can stand turn-based, give 7 a shot.
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