You mean scripts for a specific platform or a whole new script platform? for first scenario i think you need to learn the required language that the script platform is using for example: lua, assembly and so on, for the second scenario i believe with C++ knowledge you can do it, maybe reverse engineering too to reverse league client to understand AC and avoid bans.
Learn the basics from C++, also there are many tutorials on youtube i've found just by searching once!
Nowadays everything possible, it will take time and is hard to understand, but once you learned the basics its like
reading a book when you look at code.
Start small if you want to learn to program, Python is always a good option to start, there is a platform that uses Lua in its scripts and if you know Python you will realize that Lua is very similar. Once you have learned the "basic" languages, I recommend you make the leap to C# or C++
It depends, what do you want to develop a script for?
there are several ways to create scripts, you can start using AHK.
has documentation on the AHK website.
Take a look there and see the documentation, any questions, just ask