Across 1,371 ranked games on patch 16.21 in Master and above, Master Yi mains win 52.9% of their games in the jungle.
Their most common build appears in 52.4% of those games and wins 53.5% of its 719 games.
It starts 
Gustwalker Hatchling, completes 
Kraken Slayer, 
The Collector, 
Lord Dominik's Regards, 
Infinity Edge and 
Immortal Shieldbow in that order, and takes 
Boots.
One other build is played often enough in the jungle to be measured on its own.
In the jungle, Master Yi mains fare best against 
Kindred (won 76.9% of 26 games), 
Hecarim (won 65.3% of 49 games) and 
Kayn (won 65.5% of 29 games).
Their hardest matchups, the champions that counter Master Yi, are 
Qiyana (won 30.3% of 33 games), 
Viego (won 41.3% of 46 games) and 
Graves (won 42.2% of 45 games).