This article describes the odds involved. In Diablo Immortal, you've got six "primary" armor slots that only take "legendary" gems. These gems offer unique effects that have a huge impact on how your character plays. They also come in 1, 2 and 5-star varieties, and the difference between those tiers is
massive. The odds of getting a 5-star gem is 0.045% chance (1 in 2,000) which costs about $5k on average. But there are 10 of them, so in order to get a 5-star
of the one you're looking for, it's closer to $50k. Doing that for your five other slots, and then leveling those up to max, could easily cost you upwards of seven-figures.
Don't play gacha games, kids.