Play a ton and realize what is going to happen before it happens. Realize sometimes there is nothing you can do, try to help/prevent where you can. Learn not the best picks, but the safest ones. Ezreal comes to mind.
Sometimes you lose, there's no getting around that. Losing well separates good from bad in anything. I honestly felt for a long time like, "I'm not the reason we're losing, but we're still losing" and I thought I'd go up rating. I didn't actually go up rating until I identified the reason we were losing and helped my team prevent it.
And don't talk **** to teammates, ever. Not only will you eventually get banned but it doesn't help. Just try to move on and forget about it. Nobody likes losing. You're more likely to lose if everyone is pissed off. Just play more and get more experience.