I gambled one time. I accidentally tried to upgrade a common’s 2nd upgrade with only 1 common medal (50% chance) and failed. That was annoying since I meant to put 2 medals in and there’s no are you sure you want to gamble? pop up.
Meanwhile, Keylime managed to get the 3rd upgrade for his TPK with 1 Nysha and 2 Anu medals (55% chance).
I’ll gamble more in the future when I finish my lower rarity stuff.