just as thug derives from the indian thugee cult, gully is taken from the indian definition of "street". the literal translation is alley. Gully, in indian languages means dirty, street, dangerous. The origins of these words is sanskrit.
US - Keep it gully! - keep it raw/street
india - that guy has respect in the gully - that guy has respect in the streets.
The opposite of "peak". Peak means bad. Gully means good/sick/cool/top/ace/piff/naice/quality.
It also has a hand gesture, for when you really need to signal a gully thing, without words or with extra feels. You make a peak by touching your fingers in a point in front of you; you make a gully by doing the opposite, a "v" in front of you.
Ah hey bro, what's up? How was the club last night?
Dude, yeah, it was so gully *hand gesture*! We had like, 4 beers, and didn't get back until, 1:00!!
Hey guurrrlll! You look great today, I love your top!
Awww thanks babe!! Yeah, it's new. I just couldn't resist, it was so gully!!