How to make something similar to the forever pack from Pet Simulator 99?

So there is a pack in a game called PS99 (Pet simulator 99) and I am wondering how to make a system similar to the forever pack. Instead of robux, I want the system to be with a currency called Gems.

Example of the foreverpack

I just don’t know where to start, so can I get a layout on how to do it?

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