Hey Ace, my game, Feed My Affection, is built in Ren’Py and has resource management systems like this already built in. A lot of it is incomplete, but it currently has a working inventory system for resource management, and character stats for things like affection, appetite, stomach capacity, etc.
You are welcome to download the latest free built and look at the code. It’s been made fairly easy to navigate — you can check out “inventory.rpy” to see how the inventory system works, for example, and most of the code has been commented thoroughly. You’re also welcome to copy any code from it directly if you want to, although given your situation, my advice would be to use it as a learning example.