Discarding potions in lower leagues
When I was in gold league, I'd get some extra gold foil cards, specially thanks to potions. Potions double your odds of pulling a Legendary and a gold foil out of reward chests, but they're so much better in Diamond and Champions league, it isn't even funny.
I'm saving my potions for actual packs instead of rewards until I can consistently win at Diamond+, otherwise I'm losing a lot of their value. Also, I'm getting less chests, which means I'm taking a lot longer to upgrade my soulbound summoners. This isn't the right course of action for me.
Despite owning enough Monsters to climb to Gold League while renting only Summoners, I've decided I'm staying at Bronze League for now. That's where I can take the most daily chests every time. Turning off potions for reward cards ensures their value is kept for next season's packs.
Level-appropriate Bronze rentals are very cheap, too, and even more importantly, buying extra rental energy is super cheap - 2 dec per energy. After identifying and renting meta Monsters, who's going to stop me? I'll easily and consistently earn those satyisfying soulbound chests.