Sart with a Dorans Blade and a Heal Pot and just follow my rules
1. Buy a Blade of the Runed King for Lifesteal and Attackspeed
2. Boots of Swiftness for the enemy can't catch you if you are Splitpushing
3. Zz'rot Portal for Plitpushing faster and harder
4. Titanic Hydra for autoattack reset and Tankyness
5. Deadmen's Plate for Tankyness and the Passiv who gives you Movementspeed
6. Spirit Visage for Tankyness and better Lifesteal

You go 18/12/0 and pls take Warlord's Bloodlust and Bandit. Bêcause sustain isn't Yi's strenght but you can balance it with these Masteries and if you got camped Bandit is really good because you suck without Items.

5x Attack Speed and 4x Attack Damage in Marks
9x Armor in Seals
9x Magic Resist in Glyphs
2x Attack Speed and 1x Attack Damage in Quintessences

Take Ghost and Teleport

Don't mind your Team, just think that they are doing good without you. Ganks are nice but not important. Splitpush Top to T1 Turret and then do the same at Botlane. If bot hasn't a T1 anymore you push Inhib's and Nexus. If they won't Surrender, you will Oush them to Death. 1on1 isn't a Problem for you, because you are Tanky and you deal very good Damage.

Don't Mind your Team, but try to get a Penta.

You need no Skill for Master Yi!!!