I've played I, IV, VI, VII, VIII, X, X-2, XII, FFT and FFTA. However, I only beat VII, X, X-2, XII, and the tactics games.
Dont play X-2, it war horrible. i swear the game must have been made with no budget, and it ruins any coolness some of the characters had in X (BROTHER)
the highest levels i had ever had are currently in my XII game, everyone is in the 90's. oh, try giving Ashe the Masamune, and the genji Gauntlets! with haste and berserk, she becomes a mindless killbot!