Well what I would recommend for ranked is try to get maybe two champions, and get REALLY good at them. These are the champions you fucking love to death, you main them, you have 300 games on them each and they're the champs you bring out when you want to whoop ass. You have like a 60-70% or more win rate with these champs.
Get two champs like that (preferably in different roles) and try to play them all the time. But you should also be reasonably good at EVERY role, because sometimes you simply won't get the roles you want.
For me, the champion that I main is anivia. I fucking love that bird and my win rate over the last 20 ranked games I've played is 75%. I'm steadily rising in my elo (currently silver 3) I play her every chance I get.
Get a champ like that before you play ranked xD When I first started playing ranked I was not nearly as good as I am now. I got put in silver 4, then fell down to silver 5 and gave up. My win rate with anivia then was hovering around a bit less than 50%. I also made the mistake of thinking I was good at gnar when I was fucking horrible at him. I convinced myself that I was good but we kept losing because everyone else sucked.
BY THE WAY that's another thing, if you're going to improve and get better and rise in ranked you HAVE to be able to recognize when you fuck up. Don't always blame everyone else, sometimes it's your fault. Everyone fucks up, you have to be able to move past it and learn from it rather than stubbornly think it was someone else's fault.
Also, it helps to have the mentality that "we lost because I didn't play well enough". If I have a feeding bot lane, my attitude used to be "fucking gg feeding ezreal we can't win" now my attitude is "Well fuck, I guess I have to carry" It's better to not give up before the game is over, you wouldn't believe how often I've seen games we've come very close to surrendering swing back into our favor and eventually become a victory for us. I almost never surrender in ranked, because believe me, huge comebacks are possible.
AND I know that when riot has those statistics like "kind players win 14% more games" or whatever it is, you think they're probably B.S. But you know what? I found out there's some truth to it. Try to keep your team's morale up and try not to flame someone doing badly, they'll have much better odds of coming back from it and not being useless the rest of the game if you don't flame them.
And ALWAYS remember that it is just a game. TRY to have fun, and know that if you do truly deserve to be better than the rank you're at, you'll get there eventually. AND remember that, while often it will seem like you have idiots for team mates, you're all at the same elo and the other team is probably dealing with the same morons.
OH AND ONE LAST THING
DON'T FORGET TO WARD
EVERYONE should try to keep a pink ward on the map, and when you can get that blue trinket upgrade, GET IT! You can place an infinite number of those things and they NEVER time out, you can keep your entire jungle constantly warded with those things if you're spamming them (which you should be because you can have an infinite number of them) THEY ARE SOOOO GOOD AND ALMOST NO ONE ELSE EVER USES IT IN SILVER, I DON'T KNOW WHY!
xD
good luck in your elo climbing