itch.io

For sure! I'd recommend just starting off reading and messing around with some of the easier to hack systems - Fate, Apocalypse World, etc - and just tweak them, see if you get any cool ideas about how their systems might work for this idea or that idea, then go from there. It's how basically everyone I know got started, and it can be a really fun, easy and quick way to go from idea to playable without worrying about the underlying maths.

Generally tho, my process for coming up with a system tends to start with me coming up with a list of abstract concepts that I want the system to do (Be easy to teach, rely on only one kind of dice, be based on tarot cards, etc) and then spend a lot of time thinking about how to tick those boxes while also, simultaneously, considering what I want the system to "say" and how I want to accomplish that. It's a long process, and it can be super frustrating but really rewarding. But it's not inherently better than using one of the many existent systems out there as your base!