Ok so here's the idea: one of the champions first unlockable for behginning players is master yi.
Yi is a fst moving fast hitting damage dealer which is ideal for people who need to get the hang of timing certain abilities, and this guide is just for those players.

WORD TO EXPERIENCED PLAYERS:
Yes there are better things you can do with yi so just ignore this guide and do what you think is best.

What is Master Yi?

Master Yi is the champion you call on when a really anoying player (espescially low health casters or ranged dps'ers) needs to be taken care of; hence an asassin.

Things to note; Master Yi takes care of "squishy" champions BUT he himself is squishy. The result being you begin game being a bit of a risk (because Yi is a melee champion). This gives two possibilities:

1: you feed begin game keeping you at a disadvantage for the entirety of the game
or
2: you keep behind your minions only occasionally moving forward with alpha strike for gold purposes, eventually making you outlast most champions and resulting in a big advantage over other players winning the game in your favour.

note to beginning players; DONT BUY RUNES. Wait untill you A; know which champion style is perfect for you and B; wait for at least tier 2 runes because buying tier 1 gives only a very minor advantage and is a waiste of your precious beging LOL IP points.

UTILITY is the word here; try to aim for the experience increase.
why? I'll tell you; Master Yi is very dependent on his gold gained from Champion kills and he can't make enough of these untill he is level 6 (highlander is your best friend)

because this guide is for beginners i must stress that any points in the offense tree are a waiste of your time and I only added them as show off for what yi CAN reach.

follow this and yoou'll be golden

1: boots of speed; you will need an early speed boost to run away or potentially after enemy champions. this is automatically followed by
2: berserkers greaves; attack speed is what makes or breaks master yi, again an increase in speed is holy
3: build zeal and upgrade it to phantom dancer; it will give you crit chance, damage and an attack/ move speed increase; POWER is the word here; by the time you have this you will have a major advantage against all champions (all except tanks). Start earning gold and kills help your team and watch in awe as Yi kills all in his path and then runs away before reinforcements arrive.

Now you will start realising two things 1; some champions can still autrun/ teleport from you.
and 2; enemies will start getting the hang of killing you too, because you are still very squishy. This is a good time to buy

4; Frozen Mallet; it has a major health increase AND due to your enormous attack speed you will permanently slow those pesky runners. need I say more?

5; Starks Favor; by now you will be having enough of running back to your portal to heal and so a lifesteal is a must, sharing it with your team is a nice enough extra :D

6; MALDREDS BLOODRAZOR; every attack reduces targets health by 4%, you attack twice every second (or more if you activate highlander), 8% additional health takeaway per second is a very nice bonus) you will reign death.

7; Infinitys Edge; your attack speed and movement speed and survivalability are high enough now its time to end the game. With this item you can solo a minion wave a champion and the tower he's hiding behind without as much as a minor dent in your health.

alternate alpha strike with wuju style for major damage and minion killing. When you can get highlander do so, it is your major killing champion spell and will get out of cooldown as soon as you do make a kill.

Meditation is a near useless spell for this build because killing minions heals more health and additionally gives gold. It's not worth the mana or wait time.

Heal; ideal for getting out of tight spot

ghost; ideal for getting out of tight spots or for use in the event of highlander being on cooldown.

Alpha strike level 5 means killing all basic jungle creatures without too much trouble. This is ideal for some extra gold and experience or for regenerating health with your lifesteal.

Buffs are O.K. but not nessesary for Yi.

Just one thing; Kill champions who kill your allies, end their torment and remember to roam once you get ahead of the game. Laning a way to earn XP and gold not for killing champions. USE THE JUNGLE

This should give you a quick view of Master Yi's damage output and why it's great for beginning players to use him and embrace the Wuju