If the other suggestions feel too advanced and you really rather stick with an open-source engine/toolkit, perhaps give GDevelop a try? I haven't used it myself so I can't personally say if it's actually any good.

It advertises a "no coding required" system, but from some quick peeks at their youtube tutorial videos (listed in their Learn page), it looks more like low-coding, but it doesn't look too intense. It might be beginner-friendly enough to get you started. Once you accrue more skills and confidence, then you're free to pick up any other engines out there that might fit your goals better.

As for system requirement, apparently it just needs about 64-bit CPU and 1GB of RAM.

As for dreaming way too big, it is highly recommended you start with a small project. A "toy" rather than a full-on game. Gamedev is a multi-discipline field and how wide that covers depends on how complex your game is. There is a LOT to cover. Keep your feature scope small will help prevent the project from overwhelming you and scaring you away too early in your endeavours.

I hope that helps. Best of luck and have fun!