@Elforen:
Unlike a lot of other DMM games, you can still get the black units from the base summoning, though I heard base summoning leans toward giving male units. However, the difference between summoning platinum and black units from it is roughly the same, and there's no black male units (if you manage to summon a black one, you have a 1/5 chance of getting one of the ones you wanted).
EDIT:
This might be official.
Encounter (30/1):
Scroll (30%, 100% first drop), Bouquet (50%)
Feint (35/2):
Scroll (100%), Bouquet (70%)
Ambush (40/4):
Scroll (50%), Scroll II (100%), Magical Crystal II (70%)
Scrolls per day (Min: 12, Max: 18, Average: 15).
Castle Siege (60/6):
Scroll (40%x3), Scroll III (100%), Sanosuke (10%)
Scrolls per day (Min: 12, Max: 24, Average: 16.8).