Master Yi is very good in the current META with devouerer and AD and attack speed items, I recently discovered that he is extremely good with Devouerer followed by AP and Hybrid items that Provide on hit effects. I hope you have fun with my build and I hope it gets you some elo

Smite is Essential
The second spell is up to you, you can use TP, Flash, Exhaust or Ghost.
All of these are viable

Get your devourer ASAP, i like to build Skirmishers for the 1v1ing potential.
A good time to be sated is under 16 minutes under 20 minutes alright but anything over 20 minutes is pretty bad.
Guinsoo's Rage Blade is the essential item, i like to build this pretty much first thing after my devourer.
Before Guinsoo's I recommend picking up tier 1 boots for the mobility clearing your camps and getting devourer stacks quicker.
After Guinsoo's Rage blade, Build Bilge Water cutless build this item a Hextech Gunblade.
After this pick up your boots, i like to go sorcerers shoes in most games but if they have a lot of hard CC or Magic damage (AP top(Teemo), AP Mage Mid(Ryze), Hybrid ADC Ezreal/Corki)) I would go Mercury Treads. Feel free to build into Tier 3 boots whenever (Homeguards, Alacrity and Furor all all viable choices, But i prefer Homeguards for the map pressure.
Pick up a Stinger for your 5th item build this into a Nashors Tooth for the attack speed.
Build a Heavy AP item for your last item, Rabadons (if ahead) Zhonyas (For AD heavy Team comps) Abbysal Scepter (for Heavy AP Team Comps).

Pratice Master Yi in Normals a lot before playing him in ranked, Play AD Master Yi before Playing AP/Hybrid Master Yi in ranked as AD Master Yi is easier.

Pros
become a late game beast with good farm and an early devourer.
Hard Carry 1v5 when you have 5 to 6 items.
A lot of room for error with your connot be slowed ult
Drop maximum disrespect with ctrl+3

Cons
A good enemy jungler will counter jungle you early and deny farm and devourer stacks.
Poor engages can result in getting hard CC'ed and blown up

Don't Gank early as you are very weak and need a lot of farm to stay relevant in the game.
You can gank a bit a 6 but make power farming your main priority

Master Yi is a fun champion with a lot of out play potential with well timed Q's.
You can open gates and 1v5 carry in low elo.