Pros

+ High Mobility with Q Alpha Strike and R Highlander
+ High Carry and 1v9 potential
+ Easy dodging with Q Alpha Strike
+ Good jungle clear
+ Tank shredder with E Wuju Style
+ Build Flexibility
+ Strong Splitlush
+ Late game 1v1 monster

Cons

- Lack of CC and very vulnerable against it
- Weak early game with only lvl 2-3 being strong
- Squishy
- Hard to recover a bad start
- Requires a lot of practice to get a good Q Alpha Strike timing

Oh-Hit Yi

Conqueror has been the best keystone for a long time for On-Hit Yi and it keeps being. Triumph also the best option. About Legend, Legend: Alacrity and [Legend: Tenacity are the two best options. Alacrity standard and Tenacity when facing a lot of CC. Lastly Coup de Grace and Last Stand are the best options though i prefer Coup de Grace because you dont want to fight when you are low and i prefer to just slice through enemies fast and get out. Secondary domination is the best in my opinion option with Eyeball Collection and Ravenous Hunter for extra AD and Healing from all the damage you deal. Though there is one more viable option the Sorcery tree. Choose two from Nimbus Cloak to close the distance towards mobile or ranged champs, Gathering Storm for late game scaling and Waterwalking for easy Scuttle Crab contest and clear.

Crit Yi

Hail of Blades is a very solid option, with the rest of the Domination tree focusing on hugh burst and healing. Secondary you really need Triumph cause you gonna be very squishy and Legend: Alacrity for more AS.

Flash
A solid option, if you are in doubt just go for it. Great utility for engage, disengage and dodging skillshots. It is my go to for the majority of games.

Ignite
Very situational when in need for dueling power and a dominate early game. Can be an option against enemies with lots of healing but still gets outshined by Flash. Ignite can be an option but you should be very confident.

Teleport
Preferable in high elos (diamond and diamond+) where players really know how to use it to it's full potential and make plays around the map.

Smite
Standard for every jungler. Definitely go for it when jungling, don't be a troll.

Do not force ganks except if you really need to (for example, placing a rift and getting the gold from the plates). You mainly want to powerfarm but do not think ganks of a way to mess up your clear and disdain them. You maybe get a kill or if not, you will get exp for sure and some gold that you will tax from the lane minions. Usually if you do not get the kill get some minions but if you do get the kill it would be better to not touch any of them (unless your laner asks to) to prevent them from tilting.

Save your Q Alpha Strike for when the enemy flashes or uses his escape or to dodge important skillshots. Usually try to flank the enemy and just walk up to them.

When the enemy jungler reveals himself, you can counter-jungle the opposite quadrant. Or when they die you can sneak steal his buffs and make him really frustrated. Also, you can leave one small Murk wolf or one small Raptor or from the 2 original Krugs the small one to prevent the camp from respawning. This way you mess up his camp sequence and leave him behind as far as gold and exp are concerned. When the enemy jungler goes to that camp he will have to kill the small monster for little exp and gold and wait until the camp respawns again to take full advantage. If you can do this in his red buff quadrant, he will have 2 camps stalled and his buff missing, and he will be quite upset. If you get ahead of the enemy jungler you can start counter-jungling even without him revealing themselves. You will have level advantage and thus stronger smite to steal away camps. Or you can just 1v1 them in their own jungle and make them go AFK after. But be very careful about lane priority since getting collapsed and shut down can be detrimental. So do not get cocky.

Always check for enemies who shove waves into your tower when your laners are missing (dead or recalling). These minions are wasted and why not take advantage of some free gold and exp.

If you get ahead of the enemy jungler you can start counter-jungling even without them revealing themselves. You will have level advantage and thus stronger smite to steal away camps. Or you can just 1v1 them in their own jungle and make them go AFK after. But be very careful about lane priority since getting collapsed and shut down can be detrimental. So do not get cocky.

A very helpful way to look at lanes is to unbind the option “Select Ally 1”, “Select Ally 2” etc. from the F-keys (F1, F2, F3, F4) and bind them in easier to press keys to be able take glances at your laners and gather info about the lane state, if it is gankable, etc.

When counter jungling try to place some form of vision deep into the jungle to be able to keep track of the enemy jungler, while protecting your team and giving you the opportunity to spot him and make some sort of play around the map either is an objective, a dive or even a simple gank.

As Master Yi your main goal is to snowball hard into mid-late game. Start the game by farming, try to sync your camps to maximize the gold/exp outcome. You can solo drakes pretty easily though i dont recomend it before 11 minutes due to the fact that you will be very weak and will take a lot of time and resources. After 11' you can solo them without losing too much time and messing up your farm. Also try to track the enemy jungler and counterjungle for more gold/exp. Exp if you see enemy jugler top go counter-jungle bot and vice versa but be careful about lane priorities. Once you get your Kraken Slayer Kraken Slayer you start dealing some serious damage and will be able to melt epic monsters like herald, drake and baron. Also try to contest Rift scuttlers as they provide a nice boost of gold and exp in the main pool that the clear provides. Be careful though not to over-contest the Crab as this can lead to your death and thus get shut down early. Watch out for laners rotation/roam and also dont risk it against early game monsters like Graves, Rek'Sai.

As the laning phase ends you can either start joining fights ans follow up your teams engage with an R to dive into the backline. Or you can abuse the fact that you can easily 1v1 or 1v2 a lot of champions and go split pushing. But you are the jungler (and i hope you do not take Teleport with you) so the enemy could force a 4v5 fight and take Baron Nashor or Elder drake or Drakes overall. So be careful not to split too far away or not to split at all.
In mid to late game you start taking the game in your hands (and back) so you got to be careful not to take risky fights. Let your team peel and flank from behild to wreck enemy backline. Look for fed/squishy targets and eliminate them. Then go for the tanks and gg.
Try to perfect your reflexes using Q Alpha Strike to dodge high damage abilities and CC. Once you get 2-3 times you can also solo or duo baron but this has to be done very precisely and in communication with your team. Also try to do it when all your team is alive so everybody benefits from it. Also you wanna start working towards the dragon soul as it is very beneficial to Yi no matter which one you get. You need everything you can get to help you survive when you dive the enemy backline.

Master Yi gets countered by enemies with lots of CC and Burst like Kha'Zix and Rek'Sai. So you mainly want to ban these kind of champions to make your life easier. Though if the enemy team don't ban Yi usually i focus on keeping one counter champion unbanned in case the enemy picks him.