Not sure if this is something i shouldn't have had to do but i thought i would share my fix. Was trying to play gba pokemon games and the only one that wouldn't give a blank white screen was ruby. Found some threads about it but bassically if you put this game_config.txt file in your /home/pi/pimame/emulators/gpsp folder these and other games will work. https://github.com/DPRCZ/gpsp/blob/master/game_config.txt
Not sure if this helps anyone but thought others might want to play these pokemon games as well.