I'm a Gold II jungle main on NA. I like Hecarim because gotta go fast.
Hecarim is a late game carry jungler with no CC but an extremely high amount of tankiness due to Spirit of Dread and damage due to his item build and all 3 of skills.

Pros:
Decent early game ganks
Late game monster
Innate tankiness
Can build damage and still tank like crazy
Easy to play

Cons:
Extremely hard to come back after being shut down
Very item dependent so your lanes might be starved of gold

greater mark of armor penetration Allows you to stay relevant late game with your Rampage damage
Greater Seal of Armor Is pretty much the only good seal
Greater Glyph of Scaling Magic Resist Gives you defense against AP champions since MR options are horrible
Greater Quintessence of Movement Speed works well with Warpath

Awareness since Hecarim scales really well with levels.
Vampirism gives Hecarim even more sustain in the jungle and teamfights.
Mastermind allows you to exhaust/ghost targets for more successful ganks more frequently.
Meditation because Hecarim has huge mana problems.
Wanderer so you can get to a lane and run around your jungle faster.
All other summoner spells are explained in the notes section.

Onslaught of Shadows provides you with an escape/gapcloser so Flash is not necessary.
Ghost works well with Warpath, giving him a burst of bonus AD which can be extremely useful in a gank to burst down your target.
Hecarim has no CC other than his ult so Exhaust can be taken instead of Ghost to add more CC to your team and gank CC-less lanes since Devastating Charge can be used as a poor man's Ghost.

40% CDR is key on Hecarim because of Spirit of Dread, in addition it lets you spam Rampage and run out of mana even faster. At least you'll get more passive procs out of the Spirit of the Elder Lizard.
In my build, I reach 40% CDR using Spirit of the Elder Lizard or Spirit of the Ancient Golem paired up with Iceborn Gauntlet and Spirit Visage.

See the notes section for important info about the item build.

Sunfire Aegis is great for split pushing, it deals a decent amount of damage to people standing around you while giving great stats for tanking. This is a good choice if you don't want Thornmail and a Randuin's Omen is built.

Iceborn Gauntlet and Spirit of the Elder Lizard work very well with Hecarim due to the fact you can proc it constantly because of Rampage. Use the Iceborn Gauntlet proc to push towers faster. These two items allow Hecarim to still deal a ton of damage lategame despite building tanky.

Randuin's Omen slows down everyone in an AOE, so Hecarim, who charges in with his Onslaught of Shadows loves this item. Attack speed slows are key against people with on-hit effects such as Vayne and Kog'Maw so getting this item is a must against them. You should only have one of these on the team though, due to the active.

Thornmail is a selfish item and should not be bought unless your team already has a Randuin's Omen and/or Frozen Heart. Preventing damage to yourself should always be more important than dealing damage back.

Locket of the Iron Solari should be picked up if you chose to skip out on of the core items and need 10% more CDR. Someone on your team should pick this item up as the shield it provides is invaluable, in addition to the great stats it gives to just about any bruiser.

Runic Bulwark must be built if no on else on your team will. THIS IS KEY AGAINST AP COMPS.

MR isn't that good IMO so I'd just get a Warmog's Armor vs. AP, however you can build a Banshee's Veil and/or Maw of Malmortius if you feel you need more MR than the Spirit Visage provides.

All of the items in the offensive section of the build should never be built unless you're so far ahead that you just need to build some random items.

Spirit of Dread is taken at level 1 because otherwise you'll finish Blue with a low amount of HP unless you get a really good leash. This is also maxed second because you don't need it too much early game, but this is what makes Hecarim a late game monster in teamfights.
Rampage is maxed first because its your main damage tool for clearing the jungle and ganking. DO NOT SPAM THIS SKILL IF YOU ARE NOT HITTING ANYTHING, you will run out of mana very fast and won't be able to do anything.
Devastating Charge is a one point wonder and leveling it doesn't do much. Reduced cooldown on Spirit of Dread is much more valuable and so is the damage on Rampage. Use this skill to run into the other team 1v5, cancel a channeled skill, or knock the other team's carry into your team, this usually occurs after using Onslaught of Shadows unless the other carry is way out of position.
Onslaught of Shadows is your ultimate, put points into this whenever you can, use this skill to disrupt a teamfight, this can peel for your carry or mess with the other team's peel for their carry.

I usually start blue buff, then wolves, wraiths, red buff.
However if the other team has someone like Nunu & Willump, Udyr, Lee Sin, Shyvana I'd expect to get counterjungled and move onto red buff immediately after I do my blue buff.
I would usually back once I get 800 gold so I could pick up a Spirit Stone, Boots, and sight ward.
ALWAYS WARD YOUR BUFFS if you are being counterjungled or THEIR BUFFS to counterjungle them.
If you see the other jungler in a lane far away from their buff, steal it if possible.
Always save your Smite after your first couple of clears. You need it to secure Baron and Dragon .

These are the standard ganking paths that any jungler can take. Although its impossible to gank a properly warded lane, most lanes generally won't be properly warded and this map will help you circumvent wards. For example, coming from blue side, ganking top lane, going the path orange, purple to cyan or pink, you'll be able to circumvent all the wards in the river, but you'll still trigger the tribush ward. However, depending on how pushed the enemy laner is, you can probably kill him still.


Use Exhaust on the enemy laner if you need more time to get the kill and you need to CC the target. Its extremely important to exhaust the enemy laner if you're ganking for champions like Fiora or Nidalee. They have no CC of their own so chances are, you'll have to exhaust the other laner to have enough to take them down, otherwise they're likely to just get away.

This is a short section but I had to put it in because I don't see enough people doing this.
IF THE STRONGEST PERSON IN THE GAME IS ON YOUR TEAM use your Devastating Charge and Onslaught of Shadows to protect them and get whoever tries to kill them off.
IF THE STRONGEST PERSON IN THE GAME IS ON THEIR TEAM use your Devastating Charge and Onslaught of Shadows to kill them, and Spirit of Dread to make sure you don't die.
ALWAYS STAY NEAR YOUR TEAM OTHERWISE Spirit of Dread IS USELESS.

When ganking, don't forget to use your Ghost to get a burst of damage onto your target. Don't bother using it though if its against someone who can just get away from your gank like Vladimir or Singed.

Once you get Onslaught of Shadows, your ganks become much stronger. Use the side brushes in top and mid lane to your advantage. You can run into the bushes, then Onslaught of Shadows the other laner(s) and Devastating Charge them into your team. Don't forget your Ghost for tons of damage.

Comment about what you think I should improve in the guide, I'd really appreciate it.
I decided to be vague on a lot of points in teamfighting and jungling because there's specific guides for those and the subjects aren't really related to Hecarim, even though he's a jungler.