Well firstly there are sections you need to cover, so i shall title each section:
Map Editors / Script Editors / Trainer Editor / Pokemon Editor
Use NDS Map Maker
Graphics Editor
As with many other DS games, use either CrystalTile2 or EveryFileExplorer
Sound Editor
To Edit SWAVS (Wave Audio for Instruments and Poke-Cries), or SBNKS (Sound Banks) - use Nitro Studio
To Edit SSEQ files, use a any midi editor with functions to add midi events (Anvil Studio), and for loop points, add loopStart and loopEnd
I could work with the sound files as they can become quite complicated.
BTW - Edit the instruments to suit the sound banks, drums are instrument 1