Generally speaking, you're going to want +5 Mt, +15 Hit. Less accurate supports, like Berserkers may want to flip it to +25 Hit and +3 Mt. I guess Waste would also want that, but there's little incentive to use that over Celica's. Don't bother with Crit unless you're very specifically making a character with the setup for it. Enemy Luck gets so high that it's a complete waste anywhere else.
There's not really that much else to it, since forges don't have as much flex to them as the characters themselves.