Kog is pretty strong at the moment compared to most other champions that can be taken into the Farmer position, but I feel like a large part of that is the fact that his best early game build (
or
depending on how things are going) both consists of small parts that he can begin amassing even if he isn't doing that great.
Trinity is a trap-option on Kog. So is BorK (as far as I'm concerned). He should be focusing on his massive magical sustained damage and neither of those items help much there. Wit's gives him deceptively high sustained damage AND durability while Gunblade gives him a giant boost to his burst damage, sustain, and makes his Ult hit like a train. The one-two punch from Gunblade and Kog's level 5 Q is enough to make most soft targets mid-game back off or die.
If you're willing to be really crazy, Kog can skip all offensive gear other than
and go straight Tank (I'm fond of
to max out CDR) to play more or less as a ranged Juggernaut. You end up being durable enough to take anything other than sustained focus while dealing way too much damage to ignore.
I've always been a bit leery of Hurricane, however. Hitting up to three targets is great and all, but you've got to remember that it is up to three targets. If you're only hitting one guy (and if the enemy team is bright enough to spread out, you will only be hitting one guy) then it's okay at best.
Also: run attack speed reds/quints on Kog and go for Tabi rather than Zerkers. The damage reduction passive is amazing, you won't regret it when you're having a throwdown with another Marksmen. Kog has no escape and no engage. He needs to take his fights when they come to him, and that requires him to be able to take one on the chin more often than not.