Stuck in Gold 1

Hi, my name is Ediarai, and I’m experiencing more than a few problems in my final push to platinum. I’m currently a Yasuo main, (don’t flame) and I’m definitely planning on expanding my champion pool to mages like orianna, taliyah, etc. but since I’m not confident in most of them except for vel’koz, I’m solely playing Yasuo in the mid lane. Now, I think I’ve been fairly consistent in my ranked games, but what would happen is that I would pretty much go on a winning streak until I hit promos, and then I’d like either 0-3 or 1-3.

This has been pretty frustrating because in my first time, Yasuo got banned and I was trying to decide who to be play when my ‘adc’ kicks in katarina and I panic and try to pick an adc, bring too late, dodging, and starting off with one loss. Next game, Nasus goes 0/2 and then disconnects, and in the last game, the enemy Sion jungle goes 8/0 and carries the game.

I am fully aware of my own mistakes during my games, but I’ve been noticing that my main problem is closing out games. How do you efficiently end a game when the enemy team clears every wave that comes down mid, resulting in an unfavorable situation? I’ve tried to go for early barons when the game is snowballing, but my junglers have failed smite on several occasions and throw the game completely. Any help? I main Gnar in the top lane and have been pretty successful in that department, but I need to learn an ap top laner, and just expand that champion pool in general. Suggestions?

Edit: disregard my low win rate on Yasuo, most it is from high-silver to low-gold. I’ve become more successful since then.