Okay one does not simply,
make a rom hack
to do it you should learn how to do it first.
first of all a List of useful tools to edit your ROM
Pokemon Game Editor (PGE), lets you edit Pokemon moves and almost everything else
Pokemon Gen 3 Hacking suite, same purpose, more compatibility
Adcance Map , Map editor, lets you insert scripts into maps
Advance Trainer, lets you edit trainerbattles.
Extreme Script Editor , obvious for editing scripts
For tutorials for beginners I recommend Anthroyds Rom Hacking Series,
pretty beginner friendly and in depth.
https://www.pokecommunity.com/showthread.php?t=369646
all of his Tutorials are learning by doing with practice and examples.
