I guess i can tell you how to practice. Since you already know how to create a card, but not know how to script it; First start with copying original cards abilities. Like Sangans for example just tweak some things (eg change 1500 to 900 or something) and try to read the script itself. After doing this quite a few times you will be able to start frankenstaining. And then you will be able to do your own effects.
PILICA <3