Hello, I am Kayncer I am 18 and from Turkey but I live in Germany and have learned English for over 7 years now - I main Kayn since start of Pre Season and have learned a ton throughout playing the game and watching a lot of Videos about him, I have been learning Kayn day in and day out to become really good with him!
I have finally played a ton to think I am ready to make this Guide for new Kayn Players!
He is a ton of Fun and totally worth to OTP, I love his Kit and he fits to my Playstyle, also he is hot and has a ton of cool voice lines :P

Pros:
Best Early Jungle Clear
Huge Item Variation
Nice Sustain
Has a lot of dodge abilities
Both forms are good
Is a possible 1v9 Machine (Carry)
Has good Ganks
Has the option between Bruiser or Assassin Builds
Good Mid Game and Okish Late

Cons:
Has a hard time Early
Can´t contest much in Early
Will loose a lot of objectives before form
Can´t get back up if behind
Is very Heavily dependent on the Item Choices to counter Enemies
If you get wrong Form wait 4 Mins (very long) or directly go the other form which can ruin your gameplan

Kayn is funny, you don´t have any limitations from where you want to gank from since his E allows you to heal a bit and move through walls, always try to move up from behind, and if the enemy has Flash up Q into him and then if he flashes away throw the W after him for a bit of Orbs, Flashes are worth a ton, maybe a bit more than the kill itself sometimes, so don´t be disappointed if your gank doesn´t end like expected, focus more on getting your targets down, no matter how many ganks fail, as long as it´s not your team dying and you getting orbs to get your Form it´s always succesfull!

After Level 6 you can start Tower diving as your Ult makes it impossible to get hit by turret shots, only go for 100% kills, you don´t wanna fall Behind!

As Kayn you Ideally want to play Safe and Farm a lot, you only want to go for safe fights and little skirmishes/ganks to gain your form orbs, you can fight enemies early that are bad at duelling like Amumu, if it´s someone like a Kha´zix try to avoid him early and don´t contest Scuttle just go to the other one, try to counter gank and counter Jungle him a lot.
After Level 6 you got your first Ganking Spike which means you should now focus on Ganking more, tho you should not force the fights as Kayn as he will easily get CC´d and defeated and you don´t want to fall behind with farm!

You should have your form before minute 14, you can force a lot of ganks with either form, if ahead force a lot of Objectives as well, sometimes the enemies are scared of Kayn and don´t want to encounter him so they avoid objectives.
As Kayn your objective is also to Pressure the enemy a lot so you need to invade and check your map quite often, you have to set the enemy Jungler as far behind as he can get, If you can´t fight the enemy Jungler yet don´t try to force it, wait for Prio of your Laners.
You want to often Secure and force drake/baron as your champ is capable of taking a lot of fights so just go all out if your team is nearby or atleast has Prio of one of the 2 lanes next to the objective.

***IMPORTANT***
If you can´t fight Drake don´t worry, lots of Teams don´t understand that Drake is a bait and not useful to contest if it´s hard to win (only for soul and Elder Drake it might be worth), tho Baron is very worth the fight, because either way if you loose the Baron and the Enemies play it well you will loose your Nexus in no time!

In the late game, you should look out for Squishy targets as Blue Kayn, as Red Kayn try to tank as much damage as possible and get the tanks low, or if the tanks fall behind take the dangerous enemies out (Like ADC´s!) so you mostly want to be close to your team or at least nearby so you can help em out, your champ is not made for solo splitting!
Pay attention to Squishy targets (or splitpushing enemies) on the map and plan an ambush so you can have easier teamfights!
Try to conquer Baron or steal it, Kayn is very good for that, especially Blue Kayn and twist the tide of the match around!
After you got Baron you should try to end ASAP as Kayn falls off late game!

You Ideally want to look at the enemy comp and not your own teams comp,

1. If there are 3 or more ranged champs you would prefer going Blue Kayn, you would Prefer to go Red if they got a lot of tanks or Melee enemies

2. make 2 rune sets for each Blue and Red Kayn, then decide before the match starts which you want to choose over the other in the certain matchup!

3. Blue Kayn = End the Game fast because he doesn´t scale that well into late game and has a lot of threats by then.
In low Elo a lot of games last long so you would often prefer Red Kayn if the enemy Comp really does look tanky

4. You get blue orbs by attacking ranged enemies and red orbs for attacking Melee champs so make sure to get the right form by hitting the enemies you want the said orbs from!

5. Again if there are a lot of Squishies go Blue Kayn, if no squishys go Red

You mostly want to start at the Red Buff, level E and move to the Krugs, then you E to the raptors, hit the big raptor, move back a bit let them gather and Q in all of the raptors, after that hit the Big Raptor 3x and walk back to the Bush and Q into them all again - they´ll die and you put a second point on Q, Go to wolves by foot and not with E, Kill Wolves by smiting the big one when arrived and Q into all of them, hit the big wolve 3x and E directly to Blue buff hit it 3x and Q back to the bush where the wolves will be one shot in, take the blue buff to the gromp and fight them both at once, try to use the walls a lot to cancel your 2nd Q, use a heal Pot whilst fighting them btw, if you are close to death and don´t think you will survive just smite gromp and NEVER forget to hit both - the Gromp and Blue Buff with Auto Attacks so the Red buff damage applies to both!(Clear should be done around 3:12-3:20) after that you can try and contest Scuttle crab, if the enemy jungler is not there yet, it means he will be top and you just take the scuttle, if the scuttle is gone look for the other scutlle, the enemy won´t have a smite left most likely and you can steal it if it´s still alive, then look to get your first cleared camps again OR look at your Map for a Gank to stack your orbs!

If you get no leash start at raptors, E to Krugs, E to red, move to Wolves and repeat the blue side Clear explained above!

Shortage to Paths: Standard Red Side - Red- Krugs (Health pot)-Raptors-Wolves (Smite)- Blue + Gromp

Fast Gank Top - Wolves- Raptors- Red- Krugs - Gank Top

Fast Gank Bot - Red-Wolves- Blue+Gromp

Standard Blue Side - Blue - Gromp - Wolves - Raptors - Red - Krugs

Without Leash - Wolves - Gromp - Blue - Raptors - Red - Krugs

Tip: You can fight red and Krugs at the same time after you got your mythic item and boots

- You can Smite people with Chilling Smite and it will make your R possible to Trigger so you can safely ult someone that way (doesn´t work with Challenging Smite)

- Whilst you get ready to transform move outside of Fountain near the turret and Nexus and transform since you get homeguard Speed Boost from transforming so you are faster than usually!

- While using E you can Q to reach over a wall shortly before your E runs out!

- You can also Q through a few walls like dragon and baron pit

- If you Q into a big wall it will cancel the second Q animation and therefore give you a faster Auto Attack

- Always have your E (Shadow Step) Ready to escape a battle that is not winnable or to gain a bit of hp whilst fighting!

- You can wait before exiting your R to get your abilities back + you can relocate whilst in R (as Blue Kayn you can even R into someone and exit through a wall next to him)

- Whilst in Your R you can Smite someone else to finish them off or slow them down

- When you go in for a Gank or a Teamfight get behind enemies and Q into the direction they need to go to cut off their path!

Why would you want to main Kayn is you´re Question?

Kayn is a Hyper Carry that only needs an small early lead to really pop off later on, he can 1v9 a ton of games, in lower elo he is perfect since most of the time you have to carry anyways and he simplifies it a lot since he scales Very well into the Mid game!

If you get your Form before minute 8 it mostly will be over for the enemy team and you can just run at everyone and win 90% of the fights that you encounter, since Kayn´s huge Powerspike is actually his form.

He has a lot of Escape tools and is simple to play, he is the best Champ to learn the Jungle with as he is forgiving to a few Mistakes you might make!

The only downsight to this Jungler is that his Early is Really bad and that you can´t really play aggresively with him before you got your Form!

Thanks for Reading, this was my first guide on this Website and I hope YOU enjoyed Reading this ;D
I hope you will love Kayn just as much as I do, He has hilarious Voice Lines and is just amazing to play!
The feeling of carrying a Game is also VERY enjoyable!

(Also I got Discord for anyone who is interested in asking me more about Kayn that they might miss in this Guide or are to insecure to ask here :) ┃ きらり <3#8049