The only cheats that I've gotten to work with the My Boy emulator are the Code Breaker ones. The AR and GS cheats either crash the game, are totally bogus, or in general are just wrong. So far, the only working cheats that Codebreaker has actually done for me have been making specific pokemon appear, changing the level of wild pokemon appearing, making a single item appear in the the My PC first slot, changing the first item at a pokemart.
I haven't tested out some of the others yet but those were the ones that work. about 90% of the codes people claim to give you guarenteed shiny level 100 pokemon with awesome moves in a specific box on your computer with ribbon codes are absolute crap. There's a deoxy's one that corrupts your data totally. I'd kick any AR and GS codes to the curb. I've tried identical ones to the Code Breaker ones that have worked for me and not a single damn AR or GS code has ever worked.