Kindred is the first marksman designed specifically for the jungle, and one of the only marksman who can viably pull it off. Kindred has extremely high damage from their kit alone, but this damage isn't instantaneous. Kindred's base defense stats are very low, and this makes them an extremely vulnerable target early game. Without the right runes and masteries, you'll have trouble clearing your second camp, let alone being counterjungled or having a gank turned against you.

Let's start with the basics:
Runes-
While others would go for pure attack damage or attack speed marks, I find that penetration is a lot more beneficial. It allows more freedom when choosing who to mark, and gives you more presence in top lane or against tanky supports/junglers.
Because your defense stats will be considerably lower than most other AD junglers, taking armor seals and magic resist glyphs is pretty much set in stone. Attack speed quints to top it off, and you should be good to go.

Masteries-
You'll want to go 12/18/0 taking:
Feast, Vampirism and Dangerous Game for the bonus sustain.
Bounty Hunter, Assassin and Precision for the bonus damage, and Thunderlord's Decree for your keystone mastery. I find that none of the keystone masteries for ferocity fit Kindred very well, and the burst you get from Thunderlord's Decree allows you to claim your marks a lot easier.

Items-
Start simple: Hunter's Machete and Refillable Potion. Upgrade them to Skirmisher's Sabre and Hunter's Potion as you can, and purchase a pair of boots following them. From there decide whether to take Warrior or Devourer. In my personal experience I find Devourer to be a lot more useful (because of the bonus damage on your passive), but some prefer Warrior as it allows you to spend more time in lane and following up on marked targets. Both are viable on Kindred, and for the most part it's just a matter of preference (though against tanks, you'll definitely want to take devourer).
At this point you should finish upgrading your boots to berserker and start on a Blade of the Ruined King. Kindred deals substantial damage without building crit, and this is what differentiates them from most other marksman. While it is still good to have crit in your final build, it is unnecessary to rush it.
Farsight Alteration is good for Kindred because it allows them to check dragon/baron and the enemy jungle periodically from a safe distance without getting brutally caught out when warding.

This is my first ever guide and while my ranked score doesn't do me justice, I hope you'll consider using it and giving (appropriate and constructive) input on it. :)