The saying "I'm so wavy" was made famous by Ty Dolla Sign's song 'Wavy'.
Saying "I'm so wavy" or saying that someone else is "wavy" means that they or you are "cool", "fresh" or "fancy". (Like me)
Guy 1: I'm gonna slap you so hard that you'll leave the Milky Way galaxy.
Guy 2: Haha, no. You can't do tha-
Guy 1: *slaps Guy 2*
Guy 2: *escapes Earth's gravity*