I'll agree that often games are out of your control, but you are still a common factor in your games. If you're consistently doing well, you should end up winning more games than you lose. If you're not consistently doing well, look at the games where you're doing poorly, and see what you can do to improve. If you have a huge lead in your lane, take towers, push the lane, then roam to help other lanes get fed. Also, and especially, BUY WARDS. If you're that far ahead of your lane opponent, you can afford to SPAM wards, which you can use to find your enemies and get your allies some kills. Hell, get a sightstone if you can afford it and still be stronger than your lane opponent. Ward up the buffs in the enemy jungle, and every time their jungler goes to take the buff, go kill him and steal the buff.
Secondly, and I can't stress this enough, Objectives > kills. DNL v C9E This challenger ranked match is a great example: at 20:30 minutes into the game (32:30 minutes into the video), kills are 8 to 5 in favor of DNL, but C9E has 2 more towers, 1 (or maybe 2) more dragon(s), and MORE CS, so they actually have a small gold lead, and even if they didn't, they'd be ahead in terms of their ability to do things like kill the enemy jungler at his buffs. DNL actually ends up winning this one, but only because their team comp is stronger, and C9E has some throws (like the one right at 20:30, where they give up a couple kills and a tower in a bad engage).
Fourth, find a champion who's not reliant on their teammates as much (ie, they can splitpush, or kite for themselves - jax is good). I don't play much ranked, but when I was B1 and was tired of being called a bronze baddie, I spammed karma mid. She wins a lot of matchups, can kite for herself, and can cc people to protect your allies who don't know how to kite.
Finally, although you can't control everyone in your game, you can duo que with someone else who's also stuck in elo hell - two people who can win their lane hard and get fed, should be able to win the game, even if the 3rd lane feeds.