I was actually saving for a step-up gacha. Had no idea this didn't happen in DMM. But it sounds like having a 250 gem untouchable reserve wouldn't be a bad idea in any case.
But the main reason I'm not rushing to buy Kugaisou is of course that I don't have the ampules to train her up anyway. I rushed 6* Lavender a bit to get helper teams to a higher level, so I could clear at least some high level time-limited content more easily, but it takes a lot of gold to fully ampie up a 6* girl that's already at a high level. Gold that I can ill afford to waste at this stage. The Nidhogg event helped a little, though not as much I expected.