Well, for starters, you play WAAAAAAAAAAAAAAAAAAAY too many champs. Focus on the ones on which you have the highest winrates. Stop playing Lux when you barely win with her when you can play Zilean or Ziggs, with which you seem to win a lot, also focus on just 2 roles, mid and adc seem your best.
Don't focus on meta champs, focus on the champs you have high winrates with, that's what will help you a lot.
2nd thing, don't stress too much (and ignore the broken keyboards behind me) on the fact that your other lanes aren't stelar from the get go, make use of your impact. If you are 2-0 mid on Zilean or Ziggs, shove the lane, gank bot or top, or help the jungler, etc, don't just focus on your own lane, roam, make plays, don't sit around. That's a mistake many do in low elos (I know, I'm there and I even did it myself), they focus too much on their own lane and don't see anything else around, losing a lot of opportunities to climb.
Also, make game plans in the loading screen for yourself, something like: "Ok, I'm Zilean mid, will focus on farming for now and harassing. My jungler is Yi vs Jax, Yi can have a hard time, so if he invades or is invaded, I'll rotate ASAP to help, will also try to do 2 man ganks with him, since my stuns and slows coupled with his DPS will get anyone dead or wasting a lot of resources getting away. My bot lane is Kai'sa + Leona vs MF + Pyke, while top lane is Sion vs Ornn, top won't really need help, but if I get Kai'sa ahead, we can win easily, so I will keep shoving mid and ganking bot to the point where the enemy bot is forced to surrender the lane, my lane opponent is Lux, so I have the better wave clear in the early levels, which will allow me more pressure."
Making a plan like that will help you a lot more than you think. Things won't always go as you planned, but having an actual plan is better than no plan, and you just make adjustments on the go.