Master Yi is an very easy champion so you can play him without problem. You can climp with him very easy so this is a very good reason to start play him. You can master him very easily since he is so simple and he hasn't really any difficult combo that needs skills.Also, it is funny when you get fed and then none can stop you. He can easy snowball so when you Master Yi don't worry about your score at the early game because after the core items ,trust me, you will carry your game. I personally like when i play him and get fed and then the whole enemy team gets upset and start flame everyone, I like it even more when I comeback from a very bad early game. If you try to learn the game ,namely you are new to league of legends, Master Yi is the ideal champion for you.

I start from red with my Wuju Style because it helps to kill it faster and then I upgrade Alpha Strike and go to golems. If you see that you are low do Smite but if you can kill them without it it's better. Then if you have Smite go to raptors. After that you do blue then gromp if you can manage that or ,if not, go to rift scuttler. Then with the healing that rift scuttler restores you can kill gromp. If you can kill and murk wolf,
Focus to power farming because the buffs that did at the jungle at last few patched ,the exp buff, is better to power farm to get ahaed at level. Gank when enemy is at a perfect position.

take it when you like a full attack speed build. It helps you to have faster the Alpha Strike so it's very good rune. It's more late-game rune and it's very good at team-fights.
it helps with your damage and your sustain. When you take that make sure to buy a lifesteal item like Bloodthirster or Death's Dance you will see your heal to go up instead of down. It is also good at teamfights.
it is very good at the 1vs1. so, it's good at spitpushing. Also, I take this when I have no assassin in my team. It helps with it because will be able to one-shot the enemy adc.

Master Yi is an attack speed champion. So, you will get attack speed items that burn the enemy (the stats and the passive of Skirmisher's Sabre - Bloodrazor). We play Master Yi attack speed because it allow us to have Alpha Strike as quick as we can, since it's cdr is reduced by every auto hit.
This is core because it gives attack speed that I said before is very useful at Master Yi and also gives some damage which an on-hit champion needs. Also, do a damage on hit (15 bonus magic damage) and gives lifesteal which makes Master Yi unkillable. What is more, it damage an enemy equal with his 12% current health. It is a very good item against tanks.
This gives an huge amount of attack speed and some damage. Although, the real re***on we take it to Master Yi is because double his hit every 3 autos. Also, gives some armor penetration (15%) and deal 15 bonus magic damage on hit.

https://www.mobafire.com/league-of-legends/build/sylas-build-for-top-mid-and-jungle-90-win-rate-the-last-m-567786
https://www.mobafire.com/league-of-legends/build/king-monkey-570431
https://www.mobafire.com/league-of-legends/build/zac-the-green-mucus-jungle-and-support-builds-568385
https://www.mobafire.com/league-of-legends/build/the-big-boss-571064
https://www.mobafire.com/league-of-legends/build/make-the-elder-jealous-you-ap-ad-tank-jungle-top-build-571623