This guide revolves around an "oddity" with the Summoner job's stats. To explain what it is, I must first explain the Magic stat.

The Magic stat doesn't increase based on character level or job level. Instead, it is based on the job and the character's innate magic modifier, as well as any gear or abilities that may boost it. It is used to calculate power of magic attacks (spells, summons, magic weapons like rods) and MP.

The FF Wiki provides these numbers for magic modifiers, I am yet to confirm them:

• Bartz: +1
  
• Lenna: +4
  
• Galuf: 0
  
• Faris: +2
  
• Krile: +3

This means that Lenna is always going to be your best mage and Galuf your worst.

This one confused me for a bit, but I eventually figured out the answer: Certain abilities boost your character's Magic, but they don't stack. Instead, the highest modifier is applied. For example...

If you give a Black Mage the White Magic Lv. 3 ability, their Magic won't increase because of their innate Black Magic Lv. 6 ability giving them higher magic. Giving a White Mage the Black Magic Lv. 6 ability will cause their Magic to increase, since Black Magic Lv. 6 gives a higher magic modifier than their innate White Magic Lv. 6.

Now I can explain the "oddity". Here's a list of jobs in order of Magic stat when Lenna uses them, with no Magic-boosting equips or abilities:

• Summoner: 61
  
• Black Mage: 59
  
• White Mage: 53
  
• Geomancer: 52
  
• Time Mage: 52
  
• Blue Mage: 51
  
• Bard: 39
  
• Red Mage: 36
  
• Mystic Knight: 29
  
• Freelancer: 28*
  
• Mime: 28*
  
• Beastmaster: 25
  
• Chemist: 24
  
• Dancer: 23
  
• Ranger: 23
  
• Thief: 22
  
• Samurai: 16
  
• Dragoon: 16
  
• Knight: 14
  
• Monk: 5
  
• Berserker: 5**

*If a job with a higher modifier is mastered, Freelancer and Mime will take on that modifier.
**The only way to see this in action is to give it an ability such as Equip Rods or Equip Bells.

Therein lies the oddity: Summon Lv. 5 has a higher Magic modifier than Black Magic Lv. 6.

This is a list of general stat-related shenanigans that can be pulled using this oddity and other manipulation of the Magic stat:

• Mastering Summoner early with Lenna is very worth it, as its Summon Lv. 5 ability maximizes any job's Magic stat and fully mastering it also gives Freelancer its gigantic Magic stat.
  
• Getting the other mages' highest level magic ability massively boosts the Red Mage to become more versatile than the original, at least until getting Dualcast and then the Freelancer becomes stronger than both.
  
• Summoners with Red Magic Lv. 3 are slightly stronger than both White and Black Mages until the respective mage's level 4 spells are unlocked.
  
• White Mages with Black Magic Lv. 6 are, at base, better than Black Mages with White Magic Lv. 6, as the former has greater Agility, Strength and Stamina while both share the same Magic stat and MP. However, Black Mages' rods are typically better than White Mages' staves.
  
• Once both Summoner and any particular type of mage are both mastered, Freelancers become much better at doing their job than they themselves do.

After reaching Karnak, you may find yourself underleveled if you haven't been doing a lot of grinding. There is a grinding spot available in the forests around and north of Karnak, where only 5 Wild Nakks spawn, but it may be hard to kill them before they attack with Fire, the cheapest option as they're weak to it and it only costs 4 MP.

If your magic-user is not Lenna or you forgot to give her a Rod, you'll usually fall just short of the group-OHKO with multi-target fire spells. Using one that fails to kill them opens you up to the ???? Blue Magic that they know, which will deal a lot of damage.

To solve this problem, simply buy Fire, train Lenna to at least level 1 as a Black or Red Mage, and then switch her to Summoner with the other class' level 1 ability. Then you can just cast multi-target Fire and OHKO them all in one go. Have all your other characters defend so that they don't waste more time with attacking. One of your other characters should be a Thief or have their Vigilance ability to prevent back attacks, as they are the only way you can be hurt.

Turn on auto-battle (with Continue Auto-battle turned on) and walk around in the forest. This will rake in large amounts of Gil and XP with the highest boosts on, and with each level-up Lenna's max MP grows higher, allowing more farming before having to return to the inn.

There are two spots that can easily be used for AP farming with blue magic, but take a ton of MP.

The first is the Black Flames on the island north of Crescent, accessible as soon as you have the fire-powered ship. Like the Nakks, these always spawn in groups of 5. They can be instantly killed with Aqua Breath. However, Aqua Breath takes a lot of MP so only use this for grinding Fire Crystal jobs.

The second is the Objets d'Art in the basement of Castle Bal in the second world. They are level 45, so can be killed with Level 5 Death or Level 3 Flare (both a lot cheaper than Aqua Breath, but the latter can only be gotten later) and reward a lot of AP. They also happen to be found just a quick walk away from a shop that sells Ethers. Make sure to bank Level 5 Death off of Page 64 from the Library of the Ancients in the first world!

Against Objets d'Art, having a thief is very important because they know Break and can thus 1-shot your blue mage if they get a back attack. However, if Break does get cast, the character will still get AP, so you can switch that character to the Berserker to get some AP in on the useless class without it wasting your time attacking.

The plan is the same for both: Have your Blue Mage with Summon Lv. 5 equipped, then have all other characters defend, them use the spell, auto-battle and run around. Since the Magic stat is part of the MP calculation, you'll have more MP and thus need to heal less.

Both of these enemies are far more dangerous than Nakks, so farm some Elixirs from the Ship Graveyard (for the Black Flames) or buy items from the shops in Castle Bal as needed (for the Objets d'Art) and watch your MP so you don't run out of MP and have everything go wrong.

Here's a quick guide to turning Lenna into a veritable god of magic. If you're using max ABP boost or are simply dedicated enough, you can get this done by the middle of world 2.

1. Start with Lenna as a Black Mage.
   
2. When Summoner is unlocked, switch her to that class with the unlocked magic abilities of that class.
   
3. Grind Summoner until mastered, then switch to Red Mage and equip the Summon Lv. 5 ability.
   
4. Grind Red Mage until mastered, then switch back to Black Mage with Dualcast.
   
5. Once Black Mage's Black Magic Lv. 6 is unlocked, switch to Freelancer with Black Magic Lv. 6 and Dualcast. Congratulations, you now have a character with dualcast black magic and the highest possible magic stat in the game.

Surprisingly, this stat oddity can impact physical classes too. There exists a pair of physical weapons in the game that are affected by MP and the magic stat.

• Rune Axe - one of the sealed weapons (calculates based on the Magic stat and uses 5 MP to add 10 attack power, probably the better of these though it can only be used by Berserkers)
  
• Rune Blade - 3.91% steal from Stingray or find in a chest in Istory Falls B2 (calculates based on the Magic stat an uses 8 MP to add 20 attack power, uses the axe damage formula)

There are also all the physical weapons that have a chance to cast magic on use like the Gaia Hammer or Wind Slash.

Additionally, the Blood Sword is a knight sword but works exactly like a staff under the hood up to and including dealing magic damage.

I haven't gotten around to testing yet, but I theorize that the Mystic Knight is going to have a field day with the Rune Blade.