Attempting to expand champion pool

I've been picking up new champions like Ahri here and there to get good, so I'm not just knowledgeable on just one character. I'd like to say I'm doing great but my match history says otherwise.

http://matchhistory.na.leagueoflegends.com/en/#match-history/NA/35562236

I'm admittedly too obsessed with my comfort zone. Long work hours don't help with the practice needed to master a new champion either. Could I possibly have some insight from other players around the boards as to expanding your champion pool?

I've played Rumble in every lane and even jungle but I like the little guy a little too much that it takes me away from possibly learning some more top and mid laners. I want to be able to master Rumble in every possible way imaginable but I also want to expand my horizons.