Ok, in every Final Fantasy there is another learning system. For example you have the system where the learn it with leveling up (FFIV) or with jobs (FFV). We also have Espers (FFVI), Materia (FFVII) and Junctioning (FFVIII). Or goes your favorite to another like the learning from equipment (FFIX) or the Spheregrid (FFX)? Or even another?
My favorite is or the one from FFVI. I found it very fun to use Espers and also learn the spells then. Also you already have the charachters that have all other abilities. They learn it from leveling up. I think is really cool. Maybe the system from FFIX is also good. The buying equipment and then learn it from that is really a challenge. Because you have to think ahead. What is going to be the next thing I am going to need