I've nevre done G but G+MDMA sounds like it would't be a popular combo at all....IMO/IME mixing stimulant drugs with GABAergics (benzos+amphetamines, benzos+methamphetamine, alcohol+amphetamines other than little bits of alcohol is what i'm basing this off of) is stupid to some extent and doesn't make much sense.....MDMA use is associated with the rave and dance club culture/scene mostly, correct? I'd assume MDMA+GHB would be harder to dance/club on than just one or the other....
if nothing else, if you took enough G to have a strong effect (i'm guessing, never done it so idk but this is my guess), it would have some depressant/relaxant effects and would dull the senses a little bit almost (like idk how to explain it, would like dull your perception of music so it wouldn't sound as good/intense, it would like make music less intense so one wouldn't like it as much?) and that kinda would ruin the MDMA high i think....the whole point of taking MDMA IMO at least is that your senses are all intensified (touch IME isn't really all that intensified....i still dont smoke menthols while rolling, and OMG ORGASM RUBBING MYSELF, yeah that doesn't happen, things will feel nice and thats it, like "wow the grass feels good on my hands" or something, not "OMG ORGAZMS FROM TOUCHING MY ARM"...like slightly increased sensitivity to feeling tactile stimulation is alll, i cant explain it who cares lol.