User blog comment:Cat.ion0/Frontier Gate Farming/@comment-26455864-20151208025635

Generally any lead like Zedus or Avant is good (Crit, spark, or elemental weakness, as you will find at least two out of these three on any good leader for damage). Overall, though, Avant and Avant work best due to amazing LS damage-wise and good attack animations. If you're going Dion leads, make sure to use pure Earth and Thunder types to make the most out of the LS.

My squad for FG, which averages 3.7 millionish (definitely not that optimized)

Zedus (Lead) - Crit/Spark buffs

Ciara - Elemental buffs, DEF ignore for stage with metal ghosts

Lucius - BB gauge fill rate, HP -> ATK conversion

Haile - BB mod, BC fill if i need it

Cyan - BC on spark to help insure full gauges (horrible delay for attack though)

Avant (Friend) - Damage from LS

Almost all have Heavenly Buds (Haile has Geldnite Axe), but I have to sacrifice some damage to insure BB gauges for every round.