Now, I know there are better junglers. But , he does have some silly utility, and his level two ganks are pretty awesome.
Runes. AS Armor Scaling C/D or MR AP quints
( I have no idea if there's a better combo. if there is, hopefully I'll find it)
go either 0/21/9, or 0/9/21
Item build. Machete, razor. I wouldn't build it into a wriggles, but you could. Boots, Kindlegem, Glacial shroud, boots2. Need tankiness? Get a Frozen heart. Damage? Icy fist. But you need lots of CD, cause at maxed level, his Q is 7 seconds, WHICH can be used to pull you over walls to other creeps. As far as skill order, W is a 1 point wonder. Trade off between Q and E. Farming more than ganking? E. Ganking more than farming? Q. Other good choices: Abyssal Bulwark Wit's End Zephyr
But get that C/D and tankiness. Oh, and stop making the mistake I am. His R is a lot smaller than you think. Or closer to you, I should say. Don't think it's Veigars. --- I just found out my disease is contagious.