Master Yi is a high mobility hyper-carry. His job in the early game is to provide lane pressure through jungle ganks. Late game master Yi excels at splitpushing, and taking out the enemy ADC an APC in team fights. It is up to you to coordinate with your team how best to employ your skills.

I like to start blue buff. Make sure to get a leash from your team, and for the love of god don't smite on a leash. Then make your way to the wight camp, kill it with assistance from smite. Move on to wolves, wraiths, red, then double golems.

Just to recap Blue>wight>wolves>wraiths>red>golems.

At this point you should recall and pick up your spirit stone/boots. Master yi does not have super effective ganks pre-6 as he relies on the mobility and damage of his ult to secure kills.
For this reason you should continue to farm till 6, at which point you should look to gank lanes.

Your first priority should be to pick up your spirit of the elder lizard item. This is due to the extra gold generation it provides in the early game. If you wait to get this item you will be behind in gold and items compared to your opposing jungler.
Once you purchase your youmuu's ghostblade, your ganks will be significantly stronger, and you will likely be the strongest person on the map if you have been ganking effectively. Take advantage of this power spike. Push towers with your team. Their ADC recalled? Head down bot and take their tower with your team. You can take towers in a matter of seconds with your youmuu's and your wuju style.

Master Yi is a fantastic splitpusher, and can take towers with ease. If you play splitpush Yi, make sure to communicate this to your team. Otherwise they will probably just rage at you for not being in the team fight as they get wiped 4v5. A good strategy to employ is to have your team either push a lane or pressure dragon/baron, while you take the enemy turret furthest from your team. This will do 1 of 2 things. Either the enemy team will engage your team 4v5, and you will be free to take multiple towers, or they will send 1 to 2 people to deal with you, while your team takes their objective and likely kills whoever was sent to deal with them.

Team fighting on master yi, like any assassin, is fairly clear cut. Kill their carry/most fed member. It is important to remember to let your tanks initiate, as you are extremely squishy, and will likely die if you decide to initiate.