I think I mentioned in another thread, but yes, character placement in groups, and group placement at start, is important. It goes without saying that you should also try to level up all characters in all groups, but most people get the wrong idea from the first two chapters and think it's all about pumping up their main party. Which probably explains why so many players on my Allies list seemed to have quit a week ago.

Equipment is important, but so is equipment slots. And to get more equipment slots will require luck, since you need to "evolve" a character with the same character (summons, map drops, etc.)

I'm sure eventually there'll be a player's guide out there. Even the Japanese Wiki is far from complete and players arguing over their theorycraft.