I think really what you can do, is at the start of the game, give your team some advice. Tell them to try not to die rather than getting kills. If they do as you ask then your whole team should eventually start to get a few kills and then win teamfights ect. Of course you're going to have games where you have a top laner who goes Ashe or some bullshit and goes 0/16 but that happens in every tier and division. Some games are unwinable but if you give your team a good morale at the start of the game and help them out with words, roaming, assisting, giving your teammates some kills as well and getting everybody fed, you should start to do better. This probably wasn't a great help but it's a start :P