Depends what you're going for. If you want multi-tiered spells of an elemental nature, Fire/a/ga are fine. If you want to mix it up a bit and add physical damage, then the second is fine.
Personally I like something like:
Weak Effect-adding Elemental Spell
Weak AOE Elemental Spell
Strong Single Elemental Spell
That way each has a reason for being - one adds effects, one damages all enemies and one does a ton of damage. So if there's an enemy who isn't weak to fire, but has a lot of HP you could hit them with either the weak or strong fire spells. The weak one would apply an effect that could be beneficial and the strong will whittle their HP down a lot. The AOE is better for groups of enemies.
But, hey! You could always have the weak one apply the fire and effect to a weapon instead. Or just break away from threes altogether~