Nice. Congrats~
My 1st few round of builds were disappointing so I took it as a sign to back off & try again next morning.
Rarest drop thing I've gotten so far is a gold recipe...w/c needs tons more to complete so it feels 'ugh'.
Sounds like you've never waited for any of your constructions so far at all to ran out that quickly.
Just finish as many stages & achievement prizes as you can to get those gems as soon as possible. Not the smartest but I actually stopped at 4 slots unlocked in the Dorms to save in preparation. I don't know what I'm saving for yet but I know I'm gonna' need it someday.