(Mismatching, no jigsaw)
Jigsaw puzzles fit together or match up upon their completion.
So, UNLIKE Jigsaw puzzles, whatever clothes, styles,or what have you Rocky is referencing are not matching.
The Rap group Kriss Kross was widely known for their very different style of dress, often Mismatching their clothing. Rocky plays off Schoolboys line, while using clever word play.
To help improve the meaning of these lyrics, visit "Brand New Guy" by A$AP Rocky (Ft. ScHoolboy Q) Lyrics and leave a comment on the lyrics box