Hey guys, whats up :)
This is my first guide that I wrote, and that also one of the champs that I kinda now love playing to.
I've always loved assassin kind of champs and always dreamt of such a champ who can choose a target and the whole enemy team knows bout it(felt like bragging "YOU're NEXT SAVE YOURSELF IF YOU CAN"). So I guess kindred is the one.
Firstly, I should tell you he is ADC assassin kind of champ, much like vayne just without invisibility. he is squishy and has hard time jungling and counter jungling in beginning of the game. You may first need to back a few times for pots.

1.Awesome damage output late game with stacked passive and BoTRK
2.Great at saving an entire team.
3.Can play mind-games with his "passive mark".
4.Can hop around and dodge skillshots(but needs high skill cap) much like vayne, Draven or Kalista.
5.Can deal tons of damage with E, BoTRK and passive.
6.Great at shredding tanks, doing baron and Drake. Again cause of his passive.

1.Squishy much like any ADC champ
2.Counter jungled easily
3.If you don't stack passive well, you fall off late game, SO HUNT!!!!!
4.Ultimate can save and heal enemies too if they are within your Ultimate radius. :(

The rune page I mentioned is standard that I use mostly, however, you can switch Armor pen. "Marks" with Flat AD marks or Attack speed marks.
You can also switch flat armor yellows(seals) with scaling HP yellows(seals).
The Blues or Glyphs can include 6 CDR blues if you wish for early CDR on Q and also if you need 9 flat Magic resist glyphs, you can use that too.
With quints, I'd stick to AD quints only.

Like I mentioned, I love assassins and so my build on this champ is more or less derived on my way of playing an assassin-ADC hybrid jungler. So, just standard 21/9/0 masteries.

Before I start I wanna say

PLEASE DON'T BUY TRINITY FORCE ON THIS CHAMP

Yes, you heard it right, no trinity force sir.
This champ has a low base AD and the trinity force gives you bonus on base AD, on top of that the attack speed and HP boost is not enough.

Stats on this champ

1)Attack speed
2)Armour pen.
3)%age health damage
4)Cooldown reduction

Jungling path well always start with the side of jungle closer to botlane.
That's all I wanna say, because it will be faster and you won't lose much HP as you already are easy to kill for jungle creeps at level 1.

PASSIVE
OMG such a great skill...... much like a free BoTRK and Sword of occult and you can also use it to play mind games on enemy champs.
How????
Let's see an example.:- mid lane is getting pushed hard. and so is top lane. I can only gank 1 lane. By marking the enemy on midlane I force him to play much more passive fearing a gank and so I can gank top lane who completely never saw it coming(except if warded.
ULTIMATE
Ah!!!! tryndamere's ult for whole team and it comes with a heal. it can be used to save allies in sticky situations and bait enemies. BUT REMEMBER IT ALSO PREVENTS ENEMIES FROM DYING WITHIN THAT RADIUS AND HEALS THEM TOO.

To summarize I wanna say, overall a great but risky pick, great synergy in teamfights and baiting people.
Can play mindgames with his passive.
A great champ late game.
Can shred through tanks and beefy champs.
A great synergy against Drake and Baron.
Needs a certain level of skill

PLAY AT YOUR OWN RISK!!!!