The GBC emulator for the Dingoo does not work, IMHO, as well as emulating the GBC through the Dingoo’s GBA emulator. I suspect it was not originally written for the A320.
The trouble with Goomba is that it can be confusing to use it. Goomba converts GBC Roms through this interface:
… and saves the all the converted games in a single file (you give this file a name, like “GBC.gba”). You place this file on your Dingoo, and launch it as if it were a GBA ROM. It’s not that difficult, but it can be a tad confusing for the uninitiated, or annoying for the lazy)
Click here for pretty much every GBC game ever made, converted by Goomba, ready for running on your Dingoo (warning, ~67meg). Just unzip and place the files where you put your ROMS (NOTE: The original file didn’t work properly. Archive is now split into several .GBA files. The A and B Roms don’t appear to work, but C to Z run fine).