Ok, I have a few questions I'd like to get some help with. Firstly, I have a tendency to win lanes more often than not. Either from kills and cs(which I need to improve on, 120@20mins doesn't seem high enough), or simply by zoning them completely. Pretty confident in my laning phase, especially with Jayce. However, I have troubles winning games. It's partly due to one lane feeding or no cooperation, but I feel like I should be able to take a decent laning phase and turn that into team fight domination. It just isn't happening.

I try and position myself as well as possible, I play fairly safe and I am quite decent at targeting the most correct opponent. But, despite this, it's a no go on the team fights and I feel like I am letting my team down. More importantly, i am letting myself down. I have been in about 7 placement matches now, and I just can't get out of bronze V, even though when I play against silvers (when duoing with a friend) i preform much the same, or better.

So, any tips on how to improve my middle to late game presence in the game? A good youtube clip or something? I just am having trouble taking hold of the advantage my laning phase gives me.

i am in no way an expert(silver 5 and only playing 2 months) but use wards to your advantage and attempt to lead the team tactically. i would say that in silver/bronze there is at least 1 liable player on the opposing team. find and abuse them at all times. then the team may leave the liability to die or they will come.for a perfect 5v4 opportunity

also, depending on your role, make sure to ping your target so the other players on your team can focus with you, not everyone will know who to target in a teamfight.