Your story is like millions of others, no different. I'll give you mine. I had a horrible promo series, HORRIBLE. Three games I had either mia mid game(raging) or mia from the start. Then the feeder games where teammates would feed excessively ,double digit feeds. In the end I had two wins out of ten games, boo hoo for me. I ended up bronze 4 UGHHHHHH. Well first I started by playing a core of champs that I was good at and could affect games, and I concentrated on just two positions in the game. Second I worked on my communication skills with smart pings. Third was ward ward ward and then ward some more. Think of where to put wards where the enemy will try to reach you from. Fourth, no matter how toxic anyone gets refuse to dip to their level( You can always mute) . Take your happy pill soldier on and stay positive for those that aren't. Fifth and very importantly watch the mini map. Always keep a third eye on that mini.
I may be spitting into the wind as I have only reached bronze 2 in two weeks and may crash and burn next week , but I doubt it. I'm getting strings of wins and consistently have positive games even when another player goes tilt toxic. You calm them down if possible and dig in. I even had a win in a 4v5 match where we had a leaver. BE THE MAN...............................................................