Build a FoundryVTT clone, with zero programming knowledge.

Hello, guys! I'm reaching out to this community for guidance on my future project, so I'll try to keep this quick. Right now, I have zero programming knowledge and have decided to learn HTML, CSS, and JS to create my RPG system on FoundryVTT. However, I've changed my mind and now want to develop a Foundry clone, but exclusively for my RPG.

My idea is to have software that includes the rulebook and allows me to play the game with my friends. I know it's going to take a lot of work and dedication, and I'm prepared for the long journey ahead. Since it's just a hobby for now, I have the time to wait.

My goal is to start simple, implementing basic rules and playing everything manually. As I update, I plan to introduce more automation, 3D dice, and many other features.

My biggest question is, what additional programming languages can I cover? I want to make this software very lightweight and optimized, as my plan is to keep adding more content and updates. I don't plan to sell it or anything like that; it's just something to play with my friends and other people.