Hello Summoners!
This is my first guide with Master Yi! English isnt my mother language. I tried my best to write in the best english. Have fun with the guide!

Pros:
- Great Mid to Late Game!
- True Damage
- Slow Resist with Ult and CD Reduction with Auto Attacks/Kills.
- Strong duelist
- Solo Drake (with Ult to be fast)
- Can reduce Damage with W and avoid Damage with Q
- Ganks can be strong at 6
- You are a killstealer (nice cleanup)
- Strong Push Potential
- High amount of Movement Speed (highest ingame)

Cons:
- Squishy when you build full AD
- Weak early game (easy to counterjungle)
- Vulnerable to stuns (Stun will kill you)
- You will be first target in fights
- Early Ganks are weak
- Hard to play a higher tiers

Ghost: Is your second chance, when you dont get a kill while Ult. Also you can gank with it pre 6 (Get Red Buff). You can Q over walls to get kills, so flash isnt needed in every situation. (More in "nice to know"-section)

Flash: Is also recommended. You are able to get out of sticky situations or you are able to steal baron/drake over walls.

Smite: Its the junglers main tool. Always needed.

I always begin at red!
If you have help, dont smite it! Use W to heal yourself and go to Wolves! After this use W to heal and then straight to blue. Smite it! (Its important you save your smite till you reached blue buff! It gives you a small amount of health if getting in fight when counterjungler arrives!) Now you are free to do scuttlecrab first or to gank. Only gank pushed lanes early! Yi has no CC and is a bad ganker pre 6. Also look for lanes (prefer) with CC in your team! Avoid lanes like Zed and Katarina in enemy team. You won't kill em :)
Go back (First Back Item Section) and look for Raptors/Kruggs. Try to reach Level 6 ASAP!

Here are some tips with Yi. There are no big mechanics about this champ. All in all there are some things to know about him.

1. His Q makes him untargetable! Use it to avoid damage from enemies for a short period of time (But its a bit buggs. Sometimes it seems so, people can affect you while Q-ing.)
2. W can reduce heavy burst. Stuns/Silence will interrupt his W, so use it against Champs without hard CC
3. You can tank towers with your W!
4. When you know someone is up to dashing/flashing over walls, you can Q him and follow up if timed correctly.
5. Try to use your passive Double-Strike and immediately after it your Q to maximize DPS.