Jokes aside, I would actually recommend you pick a ROLE first, rather than choosing a set of characters. Try and have 1 champion you can play in each role (just in case) that you feel strong with, but picking jungle, top, mid, etc, and playing it constantly with a set of 3 champs you kick ass with, studying pros who play that role, is the best way to gain ELO, get better at the game, AND have more fun (imho).
Normals are for trying stuff out, running fun lanes, and exploring new builds/strats.
Ranked is serious face time. >