Hi, I'm Jina.
갬성 is actually 감성 which means sensitivity.
갬성 sounds like when foreigners try to say 감성. Somehow it became a Korean slang word.
ex) 인스타갬성 (instagrammable: A picture that is worth posting on Instagram)
새벽갬성 (twilighting: Being so into something that you're completely unaware of your surroundings)
I hope it will help you (: