porymap VS PokemonGameEditor

If you don't want to code, Porymap is an incredible tool for making custom maps and changing Pokemon encounters.

Seems doable, yeah, especially if you have at least basic C knowledge. If you get the build tools set up, there's already some follower code available, so you wouldn't even have to re-engineer that yourself. And PoryMap can probably handle a lot of the basic edits you want to make.

You can look at the pokeemerald decomp. Instead of using binary tools like Adcance Map and HMA you are editing the source code with a simple text editor and porymap. The pokeemerald has everything up to gen8 (mons, moves, abilities). An example hack that was made with the decomp is Inclement Emerald.

Porymap is the best gen 3 map editor tool, but like the other replies imply it's for decomp hacking only.

decomp has an equivalent to advance map called porymap. it's really not all that different to use. i checked your post history and you mention having trouble with adding new tiles in advance map, i can say from personal experience that adding new tiles in porymap is very easy.

the other option i can think of is the pokemon emerald decomp. you would have to learn a bit to get a decomp working, then use pokeemerald-expansion's pokemon_expansion branch as a base. once you have that decomp set up you could just use porymap to change wild pokemon locations and make those pokemon available in the wild.

porymap!

this would be super easy to do, even if you don't want to get into the newer more complicated stuff like decomp, there are plenty of older tools out there like Pokémon Game Editor and Gen III Rom Hacking Suite that would work just fine if all you're doing is changing names of Pokémon, moves, items, trainers, etc.

Download Page Link: https://github.com/Gamer2020/PokemonGameEditor/releases

editing pokemon data should also be fairly simple depending on what you want to do. for this i recommend pokemon game editor. it has a variety of functions, but you can load your rom and pick the pokemon editor. pick the species you want to edit in the top-left. the species' catch rate is in the base stats tab, next to its other stats like HP and attack and so on. you didn't mention wanting to change evolutions, but that should also be really easy, and it's a popular edit in case you want to get ride of trade evolutions. just go to the evolution data tab and change "condition" from "trade" to something else like "level".