How to get out of silver

I've always wondered the same... About 30% of the games, there are trollers, or people who just... "feed" or suck really bad. 20% of the games, the game is a loss, either by luck, bad decision, or simply just a better enemy team. The last 50% my team wins.
With 50% winrate, I'm stuck.

I feel like im doomed, and gets in the team with trollers all the time, never having trollers in the enemy team. But that might just be a feeling I have.

Cant really help you much tho, but playing a champion you know very well certainly helps, then you can focus on the game itself, instead of learning the champion you play.
Focus farm, dont chase for kills, focus objectives, try play smart.
But in the end, its a teamgame,and you kind of depend on your team...