IMO Master yi is alright in the lowELO but once you reach higher, you won't have a chance with him, because people will know to handle
him which will make you die like a fly in every teamfight. Been there done that with master yi, in the low ELO you will most likely get either a quadra or penta every game if it goes alright.
btw, you should buy youmuu's ghostblade after statikk shiv and blade of the ruined king and they won't have a chance in early game!