Stalling in Gold 2

At the beginning of the season, I had a comfortable 57% winrate and was climbing incredibly rapidly. I coasted to Gold 2 before I started playing with one of my friends in low silver, thinking that I would play a game or two with him then continue my ascent to plat. Needless to say, my mmr took a nosedive of epic proportions, and now im sitting at barely above 51%. Where I was previously queueing with mid-high plat, I'm now constantly facing opponents my own rank with teammates in the mid silver range.

I have tried everything to carry 1v5, but even getting pentakills isn't enough to win it would seem. I'm a Rengar main and have a ton of experience and comfort on the champion, but he's rather hard to make viable in the current meta of uber tanks with insane damage outputs and cc. Most games there are 3 or more tanks, sometimes even 4 when someone busts out the Olaf mid.

What I want to know are your thoughts on the easiest way to completely solo carry games, without having to rely on teammates at all. I tried the support gig for a long while, but I can only peel for so long before poor positioning and target selection take their toll, so I would prefer suggestions outside of that role.

Side Note: I've been tilted since patch 6.3, and do enjoy a good clown fiesta, so feel free to suggest champions that thrive in that environment. I was born in the clown fiesta, molded by it. You merely adopted the clown fiesta. I didn't see objective play until I was already a man.

EDIT: I really need some replies, I've only won 1 game this entire week in ranked and it was ezreal jungle, because I didn't want another teammate playing ezreal mid and feeding harder than I ever thought was possible.