Originally Posted by Lied

When people post their unusually good rolls it tempts more people to roll/spend money and the completely horrible rolls are usually overlooked.

50 gems without getting any 5-star+ is far, far, FAR worse than 50 stamina refills, in terms of improving your team.

Yep, I warned people not to get their hopes up too much after being tempted only to get crushed some time ago, since lucky rolls are more likely to get posted.
Regarding more effective usage of gems though, personally I would still use them on gacha since I don't power game, just enjoy collecting them.