Chrono, frog and marle (double cure is useful and frog and chrono have good techs/double techs)
And I sometimes switch Ayla for Frog so I can use volt bite or charm
After I get Magus he and his techs are for ever part of my party as I kick marle out.
Frog is a healing attacker (if he ever needs help cause I'm fighting a boss I use a lapis or two) Magus techs with a gold stud equipped and chrono attack with Luminaire in boss fights and otherwise just attacks normally.