Hecarim, The Shadow of War is an excellent jungler with great gank potential, this guide includes Jungle, Solo top and a more aggresive build.

Blue-> Wolfes-> Wraiths->(tell bot you are coming for a gank) Red-> Golems-> gank bot(if chance)(recall if you wanna spend your gold)-> Wraiths->(tell top you are coming for gank) Wolfes->top for gank(if chance)-> wraiths->(tell bot you are coming for gank)->Golems -> Bot(for gank)

Then just run: wraiths-wolfes-top gank-mid gank-wraiths-golems-bot gank and over and over again

NOTE: Grab Blue and Red when you can, and if the enemy don't have a jungler, go jungle on their side, more importantly grab their buffs.

My first game with Hecarim i used these masteries, and they seemed to work just fine.

For the Jungle and solo top i went for more of defensive mastery pages since Hecarim is a tanky kind of jungler, for the more aggresive build i went for more damage.

The builds i made for you is a build that allows the player to stay in combat longer while still dealing tons of damage making him a perfect team fight or 1v1 champion.

Max Rampage(Q) at lvl 9 since it's your primary source of damage. Then max Spirit Of Dread(W) since it gives you alot of health back as well as dealing damage making it good for teamfights. Max Devastating Charge(E) at lvl 18 since it's not primarily used for damage but for the knock back. And take your ult at lvls 6,11,16.

Ghost: Gives you more Movement speed which gives you more Attack Damage due to Warpath(Passive).
Smite: For Jungling.
Teleport: For gettin around the map faster or getting back to yuor lane after recalling.
Ignite: For some extra damage.