I also started by coding gamemodes and I think it’s a great place to start; it is not all that hard to code, and you get around pretty much everything from HUD work to networking to variables to metatable functions. And all of that in a sense of a whole as it is all used in the same final mode. People might recommend starting simple with like a HUD, and while that is good too, it can feel pointless as you will likely not use that HUD for anything, only to learn, and that might discourage you.
However it will take a long time to get something good when coding a full on gamemode. Although in sort of ‘phases’ all going through each part like HUD etc, so it doesn’t feel like you’re spending too long on the same thing. Plus in the end, you might have something good to share