The easiest way to learn scripting is from the masters themselves, the programmers of the game. Just decompile a few existing scripts and you might get the hang of it.
People sometimes don't realize the basics, though, like #org tells PKSV where in the ROM to compile to, checkflag just looks up a bit in a table, etc. It usually helps if you've had prior programming experience, especially in
X86 ASM (warning- this is a VERY difficult language to learn, just learning the basics would help you with all other similar languages including pokemon scripting), or even something a little more blind like C++ or Game Maker.