Buying skills and levelling up for stats.

Levelling up for skills and stats.

Job/Dressphere System for skills and slight stats adjustment with levelling still necessary.

Learning skills from Espers/equipment, and levelling for stats.

Materia system for skills and sligh stats adjustment, while levelling still adds stats.

Drawing magic and the Junction System for the main sorce of stats building.

Sphere Grid for skills and stats.