Triple Triad Booster packs

I like to implement Triple Triad in my game, but I'd rather have the player buy Booster Packs each containing a random card instead of buying each card individually. How do I do that and if possible, can I implement a level system so that, for example, a level 3 booster pack contains cards from level three or lower.

Yep, that's possible.

Create a new item called TT Booster Pack (or something). It'll be an item you can use out of battle (like Repel), and its effect will be to give the player a random card. The item will be consumed in the process, like Repel. You can have multiple such items, each one containing a different set of cards.

A Triple Triad card is nothing more than a Pokémon species. Card number 25 is a Pikachu, for instance. To generate a list of possible cards that a booster pack can provide, use something like this:

The above code makes a list of all cards of level 3 or lower. Of course, your criteria can be different depending on the booster pack, such as different level limits, elemental types, habitats, or be a predefined list of contents (e.g. legendaries pack). You could get quite interesting with this.

Just pick a random entry in the array and give it to the player. Simple.

Thanks, but there's one problem: I have like zero knowledge about scripting. how do I use that code, how do I give the player those random cards?

You're welcome to learn how to script if you want to script. I've already told you (twice) exactly what you can copy, and given you the majority of the code you'll need.