Do you run the daily 2 type manju missions?
They are a great way to run out of gold while getting manju.
Grinding something that drops the 80 Stamina Secret Garden Quest will get you Manju and Gold (Stage 12 maps, Event or Reissue event that drops that stage).
It has 10 soul gems on it too on DMM but they just added that recently so don't expect that for about a year or so.

I am in danger of running out on DMM because I keep getting units that are great if bloomed but underwhelming to downright bad before that.