Yeah, sounds like you're having a bit of a rough streak there. I actually just started a new playthrough myself to test some new features, and I've already found around 15 diamonds just from chests and digging around the granite/lava areas. But I get it, RNG just refuses to cooperate sometimes.
As for gambling your quartz away... I mean, I won't stop you, but I’ve never hit the jackpot myself, not even once.