Ranked in this game is a literal coinflip

Hello, I am a fairly new player. I started playing about a year ago and I have to say that ranking up in this game is seriously flawed. I have been bronze IV for months. I just finished another failed promo. Game 1 - Udyr jungle. I went 16/9/10 with 314 cs (Most cs on both teams) Got an S and lost Game 2- Urgot jungle, I went 14/5/6 with 241 cs (Most cs on both teams) Got an S- and lost RESULT*** Failed promo's*** I tried as hard as I could to carry. Ganked constantly. Kept lanes pushed. Had dumpster tier players. Lost my promo's. How can I progress??? Yes players like TfBlade consistently make challenger with high winrate yda yada B.S... I ONLY WANT SILVER. Do I need to be a challenger tier player before I get out of bronze??
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