In FFII, your actions will determine how and which stats are increased. For example:

• You attack -> your Strength and affinity with the type of weapon increases

• You use White Magic -> your Spirit and that spell's level increases

• You use Black Magic -> your Intelligence and that spell's level increases

Stuff like that. For the HP and MP you basically just need to lose part of it in order for them to raise. This does include hurting yourself, just so you know.

The spells will level up even if they don't do anything (i.e. using Life when everyone is alive).

But apparently the Pixel Remaster has made it so you don't need to mercilessly hit yourself so much to raise HP.

Straight out of the manual, this is the specifics of the stats growth of FFII.

I'm currently playing it and from what I understand, stronger enemies level up your weapon/magic levels faster.

Example: using Cure multiple times will level it up. Same for different spells. Attacking levels up weapon level.

Using spells increases your magical stats, attacking/defending increases physical stats and HP can be gained at regular intervals if you have the boost turned on.

I still don't completely understand it but that's what I've figured so far.