Finally made it out of Silver and into Gold for the first time ever. I started playing late Season 2 - Started playing ranked Season 4. Silver 2 was the highest I've been ranked in any previous season.
Note this is my experience. The formula for you might be different.
Game knowledge (including mechanics)
Playing champions you click with
Short circuiting losing streaks
Every piece of knowledge about the game or game theory adds up to gestalt that lets you develop a formula that increases your odds of winning. The most mechanically sound player is going to struggle when they run into the limits of their knowledge.
It is a layer cake and the reason you experience so much variance in your games even when the participants are of roughly equal skill level is that they all have different and incomplete pieces of the puzzle that is League in their heads.
You've got the kickass laner that rotates to your lane only to dive your lane opponent under their turret while t…