How to get better in Ranked

My aquaintaince told me that ranked isn't that different from normal when I asked him about ranked. Now that I've finally hit 30 and tried ranked I've realised it might have been the greatest lie someone ever told me. I have considered myself an okay-ish player while I was playing normal. Now I understand that I am a terrible player. I've never been so ashamed. I want to get better, but I don't know how. I've been playing support, bot and jungle today. In only 2 games have I performed with a tolerable KDA, and I only won 1 out of 5. I don't know what to do or who to ask. At least once players in my team yell at me and tell me to uninstall, but I know I will never achieve anything if I won't work hard. If only perhaps there was an understanding player who could give me advice? As a bot Teemo, everything seemed to be fine until I went to ward a bush, then Alistar jumped out of the bushes( a similar thing happened to me when I was playing Janna, CCed me and killed me. That was just one death, but then I was assaulted by a fed Syndra who ganked my lane several times. As support I kept trying to defend my ADC, and I actually got 2/6/12 on Janna, but still my teammates told me I was awful( might have something to do with me not playing support in blind pick. IpI let my ADC farm to avoid their rage. Many of my deaths seem to have come from me trying to ward bushes, and then being attacked from there. Also, in many cases I seem to have died when engaging in a team fight. My constantly lagging Internet doesn't help. As Soraka I tried to stay away from the bushes, yet I still kept dying from teamfights and others chasing me. I tried always following a teammate, it didn't help.**** I am ready to provide replays of the matches later if someone actually agrees to help me( I have LoL Replay installed). I am tolerant to criticism as long as it is not offensive, and I am willing to listen anything you have to say. I just really need an advice, and I don't know whom to talk to. I don't want to go to Elo hell.
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