About E Spheres
They generally lean toward debuffing or raising stats following inflicting debuffs.
Keywords for the abbreviations below are referenced at the bottom
What is best?
Every character is different, and E spheres are possibly the most difficult to place and decide on.
Be very mindful of how often a character can inflict a debuff, as many of these trigger based on that.
As many of these spheres inflict their own debuffs, choose one that synergizes with their kit. Consider what teams you will use the character in. For example, you may not want to give a 4th or 5th debuff to a character if you plan to run them with an ally that has 3 of their own.
Aura E spheres
Excellent for supports, Paine is the best match for any support that deals weakness damage.
ATK & mBRV E spheres
These are very useful, depending on the character. Seymour is the clear best for an attacker, with Auron, Kefka, & Irvine being nearly equivalent if the attacker's attack types match their sphere. Yuffie & Emperor come right after, being great choices. Eald'narche & Serah only belong on debuffing supports that specifically care about the mBRV stat.
Debuff Inflicting E spheres
These are undeniably the worst spheres in the game. Ultimecia sphere is interesting on Kadaj, and that's about it. These spheres were useful in the CHAOS era, but with the advent of Lufenia & LD weapons, characters have many more important debuffs than these generic effects.
Debuff Aura E spheres
These spheres are situationally very useful. Faris for Poison/Sap Lufenia orbs, and the other 3 being useful for characters that have an E slot but don't inflict a debuff
Other E spheres
Is situationally removing a buff actually better than improving stats? Put this on Ardyn and send a letter to the devs asking why he even has an E slot.
Keywords used under character images:
broken - when attacking a broken target or breaking them
vs broken - when attacking a broken target
on break - when breaking a target
crit - when dealing a critical hit
weak DMG - when dealing weakness damage
debuffed - when any enemy is debuffed
vs debuffed - when attacking a debuffed target
on evade - after dodging an attack
vs not targeted - when attacking an enemy not targeting that character
ST BRV or AoE BRV - when dealing single target BRV damage or AoE damage. A normally AoE attack vs a single target counts as an AoE BRV attack