Hi guys. THIS Is my GreyStone Jungle build. I've been using this build for quite a while and I can say that it is a solid build as long as you keep up the cxp going. This is an all damage build with some critical, speed, and penetration.
First, I start with beastmaster's key to get a head start farming jungle minions. Then, I get Rust Breaker (slot number 6) and max it out. After that, I get windcarver blade to increase attack speed early game (this will allow you to farm jungle faster). After you max out both the Rust Breaker from slot number 6 and WincarverBlade from slot number 4, toss your key out, and start Building next Rust Breaker from slot number 3. Once you max out your second rust breaker. Get slot number 5 (or you could just spend 3 point early game just to equip it and get that +44 physical and energy armor against basic attacks, which is helpful for ganking early game, and after you max out the first 3 cards, you can start maxing out Offensive Manuevers). Now, after maxing out Slots number 3, 4, 5, and 6, get the third rust breaker (slot number one), and then blade of agora for that 50% crit bonus.
For ability, you will want to get all three abilities as soon as possible. Then focus on his passive which will give you some health and physical damage, then focus on whichever you find suitable for the game.
With this build, you will have: physical damage, attack speed, some critical, and physical penetration, which will come in handy. Good luck, and hope you enjoy this build as much as I do using it.