Getting ready for monster book...

Monster limit varies from map to map, but yeah, for most areas 50 is a good guideline.

You can actually summon more than one of a goblin at a time, however the reactor becomes slower and slower after you've summoned a few. When you start getting 3-4 out there, it becomes tough to drop more summoning items too :p

Could you not use the old Meso Dropping trick of 000050000, but with 000000001 to spam drop the items? Then they would disappear one at a time as it summons them .