Most are good, but FFX could be a good starter, since it has voicework as a first in the series, it could more easily spur you into the FF universe (s).
FFVII is also good, as is FFIX, but FFVIII is probably the most varied in terms of gameplay (special combat system).
Of course, IV and VI are classics not to be foregone! If you can find them, that is...







