I Need Help with Making Stats Code for multiple types of stats like HitPoints plus others. And to upgrade them

I want to know if there is a simple code for hitpoints where if you upgrade or level up you gain more and the same for other stats plus speed . I have loads of great ideas, but i will try to find a way to get 1 done at a time. even though it took me about a month to ask for help here because I bounced around with ideas lol . please help . And a simple code on other parts where if you get enough of a resource you can hit a button to upgrade an object.

Use the META Inventory template. It has all of that built in. Not sure it qualifies as simple though.