I'm only 15, to get that out of the way. No biggie, we're people too. I play Twisted Treeline exclusively. Why? I like it. Enough of that.
Here's a couple pointers, so you won't get raged on by sensible human beings:
1) Stop trying to gank bottom. Especially if your team is a bunch of support characters, and they have a team entirely composed of strong fighters. I've won 53 games, played maybe 70, and every single time they want to gank. It's worked thrice. Three times we've pushed them back and maybe killed one. The cost is a delayed start, because now we're all low on health and mana. Stop it. Seriously. You're bad.
2) Stop talking in /all without something to say. /all Good luck all! or /all Nice gank, you got me!. Acceptable. /all lol run stupid, /all u suck noob, /all HAHAHAHAHAHAHHAH, are not acceptable. Shut the hell up.
3) Dragon shouldn't be killed the first time at 10 minutes into the match, after the other team is already fed. Get him early. Same with the lizard, he is easily killed at 8 for even support classes.
4) Stop waiting for someone to call MIA before you back off. You have a minimap. If it's got no enemies on it, back off. They're about to kill you.
5) Use wards, instead of complaining nobody was there to protect you. Wards exist, and may even get you a kill.
There's more, but that should help.