Hi my name is Boas, better known as HiHaaf3 on League of Legends. I have been playing league since the end of season 1 and I was one of the very first players, from Faroe Islands. (Most of you probably never heard about it)
This is my first guide. It isn't finished yet. But I promise when this guide is finished. It will be AWESOME.
It will take some time before it will be finished, as I do not have a lot of time doing the guide. But a small step a day is better than nothing. Right?

Why Volibear

I am from Faroe Islands so I like those champions that have something to do with the Vikings (obviously because I am a descendant of the vikings) these include Olaf, Ashe, Nunu and Anivia and Tryndamere. But I felt like there was something missing. A tank! You might think "But Olaf can be played as a tank" I disagree. Olaf can be very tough to kill, but if you build him full tank, you will lack damage. And vice versa. If you only build damage, Olaf will lack sustain. That's why I think he is better as a fighter. With damage and sustain.

Why you should use these runes

Attack speed Marks so you can faster activate your Frenzy

Flat armor Seals, for early game sustain.

Scaling magic resist Glyphs for sustain against AP users.

Movement speed Quints for better use of your Rolling Thunder

Core Items

These are the items, that you must buy in EVERY game. As these are the items, that I think will help you the must.
Randuin's Omen
This item, is especially good for Volibear. One of Volibear's biggest issue, is his lack of CC. Omen has a great active. That slows nearby enemy champions and it's passive "Cold Steel" (if you are attacked by a basic attack, you slow the attacker's attack speed by 15% for 1 second (1 second doesn't sound like much, but a champion with 2,500 attack speed will attack 2,5 times EVERY second)) is very annoying for basic attack reliant champions like: Fiora, Master Yi and Vayne.
Spirit Visage
Spirit Visage is also a very good item for Volibear. Because Volibear's passive grants him 30% of his maximum health over 6 seconds, when he drops below 30% of his maximum health. Combined with Spirit Visage you will regain 36% instead of 30% (not 45% as many people say. You have to do the math = 30% * 1,20 = 36%)
Anyway with CD Reduction, Health and Magic Resist, the item is a must buy.

Potions
Very important that you always have some Health potions with you, so buy some if you can afford it (no need for potions during late game)

Phage
Only buy Phage if you are destroying the other toplaner. Because in must games, you will play full tank. But sometimes, your team is very tanky. With both a tanky support and a tanky jungler. In that case, Phage could be a very good item. Later on, you can upgrade it to trinity.

Early/mid game sustain
In must cases, the enemy toplaner will play very aggressive against you. This will make it very difficult for you to farm.
So early game sustain is CRUCIAL, if you want to farm, and basically win the game.

Wardens
Buy Wardens if you play against an AD champ.

Spectre's
Buy Spectre's if you play against an AP champ.

Blade of the Ruined King
Blade of the Ruined King is an item, that you don't see that often on a Volibear who is playing top. The reason to this, is because most teams will have only 1 tank sometimes 2. It's very rare that a team has 3 tanks (top, jungle and support) If play Volibear top, and your team have 3 tanks (you included) Then I recommend you buying Blade of the Ruined King as it will increase your teams overall damage.
This item is useful on Volibear, as it will stack with your Frenzy (sort of) as you will have more attack speed, making it faster reaching those 3 basic attacks before you can active your Frenzy.
Blade of the Ruined King grants attack speed, attack damage and lifesteal + it's has an passive and an active ability.
Passive:
Deals 8% of the target's current Health in bonus physical damage (max 60 damage vs. monsters and minions) on hit.
Active:
Deals 10% of target champion's maximum Health as physical damage (min. 100), heals for the same amount, and steals 25% of target's movement speed for 3 seconds (90 seconds cooldown)