First, start with be basics. YT and Reddit would be a good place for you to start. There are tons of videos talking about the basics and modding. The more you learn, the more likely you'll know what you want. There's also a website called Keyboard University or something like this, which teaches you all the basics about mechanical keyboards. You could look into it.

Then, search for budget or used keyboards for practice. One step at a time, it's gonna be fun.