[Other] where do i start in a rom hack?

hello!
I'm new to rom hacking, and i wanted to make a rom hack of fire red, and i don't plan on changing any maps (other than random encounters), just the pokemon, the moves and the trainers (specifically their teams).
but i need some help on where to start. I'm not talking about what to do in the hack, i mean how do i start the hacking? in the rom? the emulator? the tools I'm using?
the tools I'm using are G3T, NSE and gen III suite, the emulator I'm using is VBA, and im on windows. I also have emerald as a backup in case fire red doesn't work out
I would also love any advice on what tools to use or what i absolutely need to use :)

Get A-Map to insert scripts to OWs.
Get XSE to write scripts to OWs.
Get A-Trainer or Hopeless Trainer Editor yo change trainers.
I don't recomend to use G3T for Pokemons. But it's perfect for adding and changing moves. So you can get PGE, G3HS, YAPE. For the changing sprites I recomend A-series.
You WİLL need unlz so just download it.
Get a hex editor. (I recomend Hex Workshop or HxD)
This is your first hack do you probibly ruin smt so back up everyting.(Your rom, sprites, scripts etc.)
If you don't want to use assembly you can use Jpan.
If you don't want to waste your tine use MrDollSteak's patch. (Use Lips or A-Patch)
If you want to watch videos about it there is Aspiring PokeTrainer,Anthoron and many more.
So welcome to the rom hacking I hope you enjoy.

Qmer kaca said everything but check this out too
https://www.google.com/url?sa=t&sou...FjAAegQIAhAB&usg=AOvVaw0KYVLTRjDunN777eL5lJio