Hello, I play Master yi quite a while for now and i wanted to share my build.

Here's a picture of my score's with Master Yi.
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First, you can lane or you can go mid it's your choice but as Yi don't play too agressive at the start.

Now for the item build: first you go with 7 hp pots, 1 mp pot and 2 sight wards then go for sorcerer shoes or go for morellonomicon for the cdr,then make an lichbane for the proc on next basic attack after your alpha strike.
One of your final items will be GA or zhonya's it depends on situation, first of all zhonya's gives armor and ap and can save you out of some situations, GA gives u armor and magic resist so it depends in what situation u are and what u need the most.
Last item will be voidstaff for the magic pen.

In my opinion Master yi is one of the easiest farm champions.

Use your alpha strike for harassment and try to get the upperhand.
If you have hard opponents farm passive and use your alpha for dodging skill shots and clearing minion waves.