I donīt have a fixed party, I always put Ayla and Robo, and at the third character slot Lucca, Marle or Frog >__< More often Lucca.
Ayla with her strength is always a great fighter against magic users and at the blackbird. His ultimate weapon is amazing, i really love it. Her techs are really powerful i think =O But I prefer using charm to steal some items :3
Robo can heal, use magic and powerful attacks, all in a character *__* The first time i played it was my secret weapon ō.ó
Frog is a Robo2, but since his physical attacks arenīt really that powerful i prefer to have Robo.
I actually dislike Marle, but I canīt deny his job as a healer is great, and she has the useful Haste with her ^^ But in a battle with monsters she is really nothing but a support.
I love Lucca, she has a protection skill and huge-damage magic skills like Flare *__* And her weapon can be terribly useful.