Tbh you can do very well with Yi with a bit of game knowledge and carry yourself to diamond... provided you know what to do, when you can fight x or y, your powerspikes, the good calls to make, etc.
Yi's the kind of champion where you can stop thinking that much about mechanics (there is still a little bit to learn, how to reset auto properly and fast with W, and then it's decision making when is the best time to use Q,W to dodge or tank something) and try to see the bigger picture. Though you'll be farming a whole lot, I suggest you try to watch a lot what's happening in the different lanes while you farm. I usually take TP-smite and go farm mode. And sometimes there are good opportunities for TP ganks. If you want to have the best success, you kinda need to farm heavily until you get strong. I personally don't get rageblade and get botrk instead. Typically when you have 
+
or + 
you can start really having a strong impact in ganks and go looking for kills/objectives.
Yi is extremely good when you don't trust your team and want to carry alone. By his nature, he doesn't really rely on any support from his team and can splitpush or try multikills with his resets when he's fed. He's one of the best champions in lower elo to hardcarry.
For items, take devourer (must buy, synergy with E's true damage is absolutely insane), one or two offensive items, defensive boots and tanky stuff.
The common build looks like 
I personally prefer 
. Higher damage, lifesteal. Better to snowball if you're fed, but quite less tanky overall.
