blame lafate then, since he didnt specifically mention box expansion first. but after some time I came to the conclusion as to how to use my SCs:
50 SC -> roll for early unit. save up to 50 (because I dont use as many and I dont buffer as much as lafate), then I completely ignore summons until I have max box expansion (because of stampcard, it's now a good idea to save up to 50, then split between bursting for box slots and for event expenditure), save up to 50 again and throw 30 for 2nd barracks and rest on events, and then the rest is free-for-all.