You first need to choose a platform you want to build script in. There are some famous ones, which I can't give a name. You need to select a platform just because you will use its libraries and coding language. Without a platform, you need to manage all injecting and antibypass stuff which are a damn huge labor.
Then you gotta learn the coding language your platform needs. Basics would be enough i believe, also you'll need to use the libraries of those platforms which provide you a bunch of "ready code schematic" i could say. But nevertheless, it's hard to get in those platforms. Just use this forum's windsharp.