Stats/Levels and what they do
April 4, 2017
15:18
First off, your stats in FFV are going to remain static throughout this playthrough.  Your character's base stats (determined by who they are), +/- the modifiers of the class they're in, are going to be it.  They do NOT change on level up; all that changes on level up is the gaining of some additional HP/MP and some impact on formulas.
Strength: Strength is used behind the scenes, alongside level, to determine the attack "Multiplier" (See Damage Formulas).  Essentially, those with higher Strength will find their damage increasing at a much faster pace and to much greater amounts than those with low Strength.  Because its role is multiplied by level, the value of STR boosts increases at higher levels, but at low levels/low amounts, a STR boost may not even change your damage. With that said, more STR = more damage for almost (ALMOST) every class.
Stamina: Stamina serves two purposes: Determining your HP, and determining the amount of HP recovered under Regen.  Your maximum HP is entirely determined by your base STA and level.  Not that this is your BASE Stamina, not counting Stamina from equipment.  Thus, while Stamina determines the survivability of classes alongside their equipment selection, Stamina as a stat on equipment is, in practice, completely ignorable.  It won't even be listed for gear in this guide as a result.
Agility: Agility does two things.  First off, it's used to calculate your ATB.  Specifically, every time a character acts, their ATB is reset to an amount based off of their Agility and Weapon Weight (as well as influencers like Haste and Slow).  This means for most characters, Agility doesn't matter too much - but stack a bunch on an already fast class and watch them get more turns than anyone else.  Secondly, certain weapon/attack types: the Geomancer's Bells, Ninja's !Throw-only weapons (such as shuriken), and the Chicken Knife significantly increase their multiplier based on Agility, the way that Strength does for other weapons - except in ADDITION to what would normally be used.  This can actually lead to several of these weapons being surprisingly powerful.
Magic: Magic functions basically the same as Strength, but for Magic spells.  It also influences your MP, though like Vitality & HP, equipment affecting magic does not change your MP.  Still, magic bonuses can matter quite a bit for dealing out more magic damage, and get better and better as your levels rise.  Note also that the Geomancer's Bells and the various Rods actually use Magic to determine their power instead of Strength… although unfortunately they are limited by weapon power.