This is the build I use for Volibear.
I have been playing a few games with him, and I noticed that Volibear is actually a very strong champion, both in the jungle and solotop. I have been playing him mostly solotop, as he is almost unbeatable there. My tip is, don't play Volibear AP. His ratio's are LOW, and he is much better off going full Tank with a little bit of AD.(Volibear has just came out, and this is my first ever Mobafire build, so don't expect this build to be totally perfect. As I said, this is how I play him, and I have been doing well with this setup.)

Pros:
- Very good at the solotop lane.
- High sustainibility due to his passive.
- Deals tons of damage with Frenzy.
- He uses lightning.
- He is a bear!
- Awesome Jungler

Cons:
- He is really slow, you have to be close to someone to be able to do anything.
- He is slow!
- All his attacks are mellee based.
- Ganked very easily, especially early game, as he is quite easily killed then.
- He is slow....

I chose these runes because Volibear is a full mellee champion. He hasn't got any skills which have any range, except for his ulti a little bit. As marks and Quintesseses I use attack speed, this is really important as this helps Volibear get the Frenzy active faster, which deals TONS of damage if used correctly.
For seals I use armor, just for a bit more sustainibility in lane, and a little for the late game.
And for glyps I take Magic resistance, just for the same reason as I use the seals, more sustainibility.

My masteries are 21/0/9, I take all the extra attack damage I can take, and more damage to minions, which helps get my farm up as all his items are quite expensive. I also take a bit of armor and magic resistance, as this too helps me stay in lane longer, and be a little bit more safe against ganks or harrasment.

I chose these items because of one thing, HEALTH AND MORE HEALTH. His W skill active does more damage if you have extra health, so once you have like 4-5k health, your Frenzy does arround 1-2K damage, depending on when you use it. I also take some more Armor and Magic resistance to be a little bit more protected against attacks of the enemy's.

About skills I have just 1 thing to say. Max Frenzy AS FAST AS POSSIBLE. Even at lvl 1 with dorans shield, this beastly skill does arround 100-200 damage! Together with some basic attacks you will WRECK the enemy's. After Frenzy I kind of switch between Q and E, as they are both quite usefull, but 1 is not of a lot more use then the other. So keep them balanced.

As I said, Volibear is a new champion, so there isn't a "Best build" yet. This is how I play him, and this is how he works well for me.
Thanks for reading my build, and comment on what you think of it. I just started making guides, so some feedback on how to improve myself will be appreciated. :)