Dead by Daylight

Title. I'm relatively new to the game, only a few weeks in. I can see the power of Iridescent add-ons (silent bell as Wraith?? Woof!), but they are so expensive and rare I have no idea when to actually use them. I'd "save" them for an important game, but... it's always just random opponents, so I have no idea if the Iri would be good or if I would stomp/get stomped either way and it's a waste. Curious to hear from people who do use them, when do you decide to do it?