Find a champ that plays differently or must react differently to different situations.
Good example: Laning Master Yi. His play style is all about reacting to the opponent's abilities, and promptly dodging (Q) or negating (W) their abilities. He's a simple champ to play, yes, but his play style revolves around the opponent, and your opponent will virtually always, always be changing game per game, so in essence, you may never bore yourself as your exposing your play style to something new each game. Not to mention that, as laning Yi, his off builds are also options to role with, from Bruiser Yi against burst based teams to Burst Yi against squishy DPS teams.
Bad example: Most ranged ADCs. Until you reach mid to higher rank, ADC is just a mehtacular role in terms of gameplay diversity, imo. Some are fun to work with, for example having to decide between Burst Graves or DPS Graves, but others honestly just feel like doing the exact same thing over and over again.