Hey purplejaek,
There are Auto Pickup settings in Island Settings for a few different types of items, But there are also overriding settings in other devices, like the Item Spawner Device, which gives a Run Over Pickup setting for the item(s) it spawns.
From the Fortnite Devices folder you will find Devices to help with your game.
There are a few ways to tackle your idea, depending on how you want the mechanics of this to happen.
You can either use an existing Crafting Consumable for the Jewel, in which case you’ll need a Capture Item Spawner.
Or you can use a fortnite prop or create a custom prop in which case you’ll need a prop manipulator to attach to it (or contain it).
There is the RNG Device for randomness, I don’t know much about that one yet.
The capture device, is the Capture Area Device.
If you want to use a custom prop it is a bit more tricky like maybe using a mutator zone and some method to check for prop owning, (like a player changing class when they get the jewel, the mutator can trigger an event when the player of that class enters its zone).
The User Option Functions of the different devices can be pointed to each other to achieve different things like Enable, Disable, Acivate and other Events.
So when something happens it can turn other devices on and off
If your keen on verse, there is the Snippets section, which should have a random number generator snippet, which would be superior to the RNG Device and an item spawner snippet.
Let me know if you need more clarity