Help creating an upgrade system

Godot Version

4.4.1

Question

Hello, I am in the process of making my first game and am a beginner in programming. I am having difficulty in implementing an upgrade system to modify the player stats like health, damage, speed etc.
I have created a UI scene with a grid container to hold the upgrade buttons. My difficulty is finding a simple, modular way of having multiple upgrades that affect the player each time the button is pressed while also deducting the points earned.
The upgrade scene UI is a separate scene that can be accessed on the death of the player.
I would like to know if there are any guides of resources on where I can find a detailed explanation of how to implement these features.

If more information is needed please ask .
Thanks