Yoho! o/
Seeing all the people both hate and hate Ornn, I've came to realise, that it may come in handy, to explain to people how exactly does that furry ram thing work. Considering I played him very shortly, I may still be in a bit of no place to speak about him, but my point is to help newbies understand some of his basics.

Ornns kit is basicly too wide in what he needs, to focus on one thing. Q going with AD, W with health, E with Armor and MR, Ult with AP. If you focus on going AD, you will get barely any buff from other skills, and your Q isn't that important too. Your best chance is to go health + Armor/MR/Both, as they work together the best, making you a tank in the end.

Few rules about Ornn.

1. HE'S NOT GOING TO DEAL TONS OF DAMAGE
2. STOP TRYING TO BELIVE HE CAN EASILY DEAL TONS OF DAMAGE
3. STOP HOPING HE WILL DEAL TONS OF DAMAGE
4. IT'S NOT GONNA HAPPEN
5. UNLESS YOU WANT HIM TO BE USLESS

For explanation... look below.

You see, what you want to expect from Ornn is simple. He's like what Ivern was ment to be. A support. A very bulky, very tanky support. So... your ganks are not going to be as powerful as for example Lee's. Neither are you going to be as good with all your CC as Sejuani (Till you reach level 6). But what you can do, what others can't, is a simple fact, that you can tank. You can disrupt. You can overall be the Superman for your team, and not only thanks to the item upgrades. So stop trying to steal all the kills, to chase after that one half-HP AD bruiser, and go back to your ADC, save his sorry *** from being whopped. Your ultimate does wonders! Trust me! And not only that... All your skills can do wonders!

And your main advanteg - You can create items on go. At least those which are not consumables. You see, the wonderful point is the fact, that you can come on your top lane, with already built first items, whilst your oponent will have just a machete (talking about jungler). Yet, you pay in exchange for that, with overall lack of DPS, and need of clever use about your skills. Rushing in with no idea what you are doing will most likely end with you being dead. Again.

So, if you'll follow what I'm saying, you should easily be able to end up with support stats by the end of the round (for example - 4/3/23).
STOP.
CHASING.
KILLS.

HELP.
YOUR.
TEAMMATES.

Truth is, Ornn is barely ever going to be the carry you wish you had. Maybe in some rounds you will get fed, and you'll plundg that hammer into someones skull, but for most of the time, you are going to be helping your ADC, your Midlaner, your toplaner, to get fed, and work wonders with you by their side.

Overall, it's a simple path you should follow, no matter on which side you are on.

Blue -> Gromp -> Wolves -> Raptors -> Red -> Krugs/Scutler

Quick cold, good mana regen thanks to blue, and a good way to prepare for your first gank. Whether it will be on top, mid, bot, it makes no diffrence in this guide. All you need to do is learn when to help your team. And as I said, don't expect to go on the lane, deal tons of damage, get a double, leave with a flick of a finger. Expect to go on the land, and CC enemies so bad, that the laner you help grabs a kill.

ALWAYS EXPECT A COUNTERJUNGLE ON RED. Especially from mobile junglers.
Truth is, that you are not going to be a master fasta with clearing the camps. Ornns speed is somewhere in middle - Fast enough to not get surprised that badly, and slow enough not to be able to counterjungle.

Quick explenation about your item choice. Most of you may be surprised by Locket of Iron Solaris, or other support items I've put in there. But if you have had read what I've written above, you'll understand that with Ornn you do the wonders of supporting throughout the game. Diffrence is, you tank and support. So when you fight, always focus on saving your team, or helping them grab the kill, instead of lowering your field of view to that singular Teemo you want to kill. Work wonders with your ult. It's op. Really.

In most cases also you'll need warmog, considering that you don't need to go back to buy items. That said, you can constantly roam on the map, ward drake, ward baron, grab buffs, kill scutlers, save your teammates, without the need to check every now and then in the shop. Thus why Boots of mobility come in hand too. Constant vision on area (I SUGGEST BUYING SIGHTSTONE IF YOU WANT TO CHANGE ONE OF THE ITEMS), strong and bulky help from Ornn, and good sustain make you a rather wonderful jungler-support.

There it all is. How to be useful as Ornn. Keep in mind, this may or may not work on lower divisions, considering that sometimes you just can't save your team from being... well... bad. Ornn is a safe choice for higher ranks, where your team knows what to do. On Bronze/Silver you may struggle to help your team, when ADC will be jumping into middle of a TF to tank all the enemy ults.