You don't need a SINGLE POTION IN JUNGLE AS YI, just use your W, use pink to ward your red or blue, trinket before ganks to check if 'warded'.

Simply, guinsoo is needed to buff your E, after Guinsoo is stacked+your passive, it will result in this= first hit is single, second is double, thrid is single fourth is double.....(1-2-1-2-1-2-1-2), so your E is soo buffed that you kill with ease both tanks and non-tanks

Low crit chance is dangerous, rare when needed, avoid it, dont buy just shiv or edge alone.

Avoid blue smite, all the time go red smite.
Red smite give vision 4 sec 2 second you get reduce dmg from target, and for 2 sec you do impact true dmg, good combo with Attack speed build
Blue smite only 1 time dmg, no vision, just some speed steal, but you have R for that.

Why is that item needed? +200-300 dmg for 1 hit?, your E is 75-100/hit in late, and its TRUE DMG, this item is just for early and early alone.
Yes, tons of ppls will reply, Noob Fider, Dusk OP. Well it is dmg item ofc you will do kills, but why 55dmg, when botrk is 40dmg+25 as+8% curent hp.
Yi is not letality champ, he s Attackspeed champ, but ofc for fun you can go full letality(For fun alone)

If you gank, or simply go in a fight, don't Q in, walk to the target, only if target, jumps, flash, dash, Q him, if you are in 5v5 go firstly with flash if you are to avoid incoming stun(Lux Q, Morg Q etc), Q is taking 2 seconds cuz you hit at least 4 targets in a Team Fight, so flash for first kill to extend your R.

Yi is a superb damage dealer, True for non-tanks, and with the help of Botrk+Jungle item you have tons of % (4% max hp/hit+8% curent hp/hit), his E make all armor look like 0, if in a team fight you can choose to aim adc or tank who aim YOUR ADC, kill tank better, so you and YOUR ADC can kill other solo Adc, but ofc there are allways exceptions, fallow your guts from time to time.

Never GO FIRST in a team fight, never, go 3th or 4th, change up guinsoo, then go in.

Tested: in less then 20 sec with Tabi+Jg item+Botrk+Guinsoo+haft of Frozen malet+Smite, you can do nashor solo, just tell your team to deff 20 sec, and check for wards before start 1v1 nashor.

Pros:
-true damage dealer
-high mobility
-good sustainability

Cons:
-no CC, weak to CC
-squishy

He farm very easy, but i prefer to farm kills

His gank skills are low, he lack CC, but still his high Dmg can be useful at ganks

Dusk: 1 improved hit, then what? just 55 dmg?, bleah
Black C.:Why do you need to reduce target armor, you have True Dmg
Berseker Boots:Yes Attackspeed champion, but that dosen't matter you need to go +500% as
B. of Swiftness:One word: Ultimate
Boots of Mobility:Dejavu
Gargoyl:Reduce your Dmg, you Exaust yourself
Warmog:Yes, some times works, but when you go in 5v5, or you win, or you lose, you are not tank to endure pokes, you dont go first, so cut this armor off
I had allways trouble with critical %, on minions allmost all time, on enemy champions, so rare, i have a rule, OR 100% crit, or you don't have crit.

I know i have done alot of mistakes, my english is low, please forgive me.

Some won't agree my build's, but i shoud tell you, 5/8 games i do S- at least, 2/8 are A+, and 1/8 are vs tons of counters that i can't do a thing.