Getting started

Downloading Butano and building their games and examples is easy and doesn't take too much time, pinky promise.

GBA emulator

Before anything, it is convenient to have a GBA emulator at hand, so you don't have to test each change you make to your project on real hardware.

For developing GBA games, mGBA, NanoBoyAdvance, Mesen and the debug version of No$gba are recommended.

Butano can be built on top of devkitARM or Wonderful Toolchain. Both are compatible with the same operating systems (Windows, macOS and Unix-like platforms), so the differences between them aren't that big:

No$gba's exception system with *.elf files only works with devkitARM.
Maxmod's conversion tool provided by BlocksDS is more robust, so using Butano with Wonderful Toolchain could improve the playback of your songs.
Wonderful Toolchain offers better compatibility with some standard containers that use threads.

So:

If you want to use devkitARM, go to Getting started with devkitARM.
If you want to use Wonderful Toolchain, go to Getting started with Wonderful Toolchain.