The champs you play seem almost random. My piece of advice would be to main one and know him/her/it well. Then probably have 3 or 4 more than you also know how to play really well, but maybe just haven't focused as much on. Also know more than 1 role. I'm not sure what you've been playing, but I'm not incredibly familiar with what champs do best where.
I.E. I play
(Main),
,
,
,
. Of those, I play Syndra and Ryze best. That being said, with those champs, I've been pulling off any role except ADC. Jungle and bottom lane roles are a little different because it's not just farm, farm, farm, poke, farm, farm, poke, etc.
Like anything, being good at League takes practice. RTS games are a peculiar beast because they are team-based, and require strategy rather than just facerolling through to the objectives. (Go figure.)