I easily got to Gold on one account simply by focusing every game on not being the reason my team loses. That means no feeding and absolutely no going 0-5 in lane, like ever, even if you have to afk under your tower with no cs to do it. I didn't have to carry or anything and I just climbed to Gold. It's boring but effective. It also greatly helps if don't play on tilt. Don't play any more after losing 2 in a row. You may start playing again when that loss feels like a distant memory. Usually means about 15 minutes to half an hour of not playing.
They way it works is by tilting the odds in your favor because every team you play on only has 4 players with a 50% chance of feeding while the enemy team has 5 players with a chance of feeding. Over time you very easily net more wins than losses and you climb, just like that. Like I said, it's boring as fuck but extremely effective. You won't have a crazy smurf-like win rate but you do have a high enough win rate to climb.
Here's the account I did it on:-
https://lan.op.gg/summoner/userName=xelniya
Also, note that on this account, I never screwed up the MMR so I was consistently gaining 20+ LP per win. If your MMR is fucked, this method is going to be painfully slow because of low LP gains and massive LP losses.