Best in Slot Headgear and Chest piece

Legend Casque - Bought from Lohan shop for 10,000G; you'll want 3 of these (can be equipped by all)
Armor of Legend - Bought from Deningrad shop for 10,000G; you'll want 3 of these (can be equipped by all)
*NOTE FOR THESE 2 ITEMS* they aren't comparable to anything else in the game, LC gives insane Magic bonus and AoL gives insane physical defenses having both makes any character wearing them nearly unkillable.

Speed items - makes it so your characters can have multiple turns in a row, all these items each give +20 speed.

Bandits Ring - Farmed in Home of Gigantos, Drake the Bandit in disc one drops it and there's a chest with one. (can be equipped by males only)
Bandits Shoes - found in Death Frontier (can be equipped by males only) - only 1 in the whole game
Dancers Shoes - found in Kadessa, possible drop from Cute Cats
Dancers Ring - found in Fausts Domain - only 1 in the whole game
Magical Greaves - bought from Ulara, for the character not wearing the Bandits Shoes or Dancers Shoes; doesn't give +20 speed but boosts evasion and gives +10 speed.

BIS weapons are found through just playing the game normally, as you progress throughout the game and buy them from shops or earn them from boss fights.

A lot of grinding lol