Well, I guess the first question is, do you know how to program? If the answer is no, I'd suggest you try some tutorials in that regard before you even attempt to do anything in Essentials. If the answer is yes, the best thing you can do is to poke around the existing scripts and try to understand what each thing does. Once you have somewhat of an understanding of these elements, you can try modifying them into something increasingly different until such time that you're creating your own things from scratch. It's a LOT easier said than done, but with enough practice and dedication you can theorietically do anything.
I might recommend the Trainer Card as something that it relatively easy to modify. There's also a short tutorial sorta thing about creating scenes that FL did as I recall, but I can't seem to find the link in my browser history. Perhaps someone else can link you. Good luck!
