You guys agree with what I've read: get familiar with 3 champs in every role? Or is that too much for a new player?
You should get familiar with as many champions as possible so you understand how to play against them, however, you should only look to play as few champions as possible if you intend to climb the ladder. The ideal situation is to master champions that can play multiple roles. What you're saying is you want to be able to play 15 champs well.... That's too many champions to try and master. You'll never be great enough at any of them to be able to climb the ladder consistently.
Example, I am currently trying to play only Akali or Kha Zix, as I feel I can carry the hardest with these champions. I can play Akali in Mid or Top lane, I can play Kha Zix in Mid, Top or Jungle.
I have over 400 games played with Miss Fortune this season, I played her ADC the most but also went Mid and Jungle with her. I was able to carry myself up out of trash tier with MF but once League of Bruisers took charge the ADC role started to crumble and I realized that it is a crap-shoot carrying with ADC, it really depends if your support is decent or not. The winner of bot lane usually comes down to supports and junglers. The ADC can definitely carry in late game but getting there can sometimes be a problem and an ADC still needs an intelligent team to setup the team fights.
I try to roam a lot and make big plays with Akali & Kha Zix. Success is less determined by anyone else. I can gank other lanes and help them out instead of being the one looking for help.
When transitioning from playing MF, I went on a massive 5-day lose streak back down to shit tier. Found my new champs to focus on, now working back up pretty successfully. Its slightly embarrassing that I have 900+ games played and am only Silver III. Its been a roller-coaster ride. In Pre-Season I've been as low as 1k Elo and as High as 1500 Elo, then once the Leagues patch hit I had remained pretty steadily in Silver I but the 5-day lose streak took me down to Silver V. I'm now up to Silver III and intend to get back to Silver I shortly and then hopefully on to gold
My go-to jungler is Vi but I might add 1 more champ because it happens often where Kha Zix & Vi are both banned out.
So right now I lean on 4 champions: Akali, Kha Zix, Vi, Miss Fortune. I am very comfortable and confident with all 4.
I rarely support, supports can't carry, but if I'm last pick then I'll do it. Just play Taric if you have to support for a game. Thresh is OP right now but isn't the easiest. Taric is easy and strong.