Boosting is optional. It helps, but it fails. I have found that it has a sort of pattern that changes every 3 days. In other words, one day will be very few fails, next day more, last day it's awful, then good again. In the law of averages, this does level out. It has been my personal experience that it's about 5-1, maybe 6-1 on avg. In tavern I have won cards on the 10 gem pick. But since the latest patches I don't use any gems unless I see at least 3 cards I would take. Just don't spend more in tavern than you can afford. When I go I really hope for lots of spirits, and have bought the majority of hero cards that way. If you spin one it's like a bonus.

I get frustrated like everyone, but if you just take it for what it is you'll enjoy your experience better.