4+ not sure exact number, player too many games
pre nerf mord got a penta 3 games in a row, post nerf mord, then post buff mord, ashe, udyr are only champs i can ever remember getting penta with.
i have seen multiple pentas in games, think i have seen each of my IRL friends except one score a penta in a game i was in.
all of these were in normals after i hit 30. i have seen one penta in ranked from my friend playing i think it was cass mid.
and i do both sides with some bananas in the center if i can. without bananas, just one side, other side is for jelly, everyone knows this.
hope you get one soon OP best of luck to you.
EDIT: when i was playing and used to get pentas, teamfights were all the rage. now there is a lot more split pushing and i havent seen one in a really really long time.