Volarbear is one of the most misunderstood champs in the game. Most people say that he is underpowered, but that's because they play him wrong. The go top lane, or jungle. But that's not his job. Volarbear has one purpose in the game. He is supposed to make the enemy ADC wish he had played a different role. Make him wish he played a different game. Make him re-think every single life decision that brought him to this exact moment in him life, where he is playing League of Legends in bot lane against Volarbear.

Volarbear's strengths lie in his ability to thoroughly get 'em in the early game. You want to capitalize on your early strength to snowball bottom lane to a 20 minute victory. Take towers early and often. If you don't, you are gonna fall off fast. Your abilities do a ton of damage, but have high cooldowns and don't scale well with items. Because of this, your late game is super weak. After about 25 minutes, he loses most of his killing power. You become a mediocre tank with a decent initiation.

For the same reasons that you get defense masteries, you want to get runes that make you tanky. You don't scale well with offensive stats, with the exception of Arpen scaling decently with his bite ability. Since there isn't any good red rune that isn't offense, go ahead and get arpen reds. Armor yellow and MR blue is pretty standard, and movespeed quints are very helpful for gap closing, considering that Volarbear has absolutely no ranged potential.

Flash is mandatory, for gap closing. After that you can get Ignite, Exhaust or Teleport. Ignite is my preference, as its is crucial that you get kills early, and every marginal point of damage is important. If you aren't comfortable with that, Exhaust is the standard support option. Teleport is also very strong with the addition of Enchantment: Homeguard boots for super scary ganks out of nowhere.

The Relentless Storm - This ability can activate once every 2 minutes, and restores 30% of your hp. Very strong against enemies without a strong sustained damage to finish you off, and very useful for tower diving.

Thundering Smash - This is your scary ability. You run at 'em, you get 'em. Not much else to it.

Frenzy - This is your kill 'em ability. This does the damage. Bite 'em when they are at ~25%, free kills. Max this first.

Sky Splitter - Slows stuff. Max this second. This ability doesn't have a casting animation, so use it as you are gap closing on someone to slow them and secure the flip.

Stormbringer - Gives you good sustained damage, it does more damage than people expect, so you can usually kill people who want to go toe to toe with you in the early game when your ult is up.

Volarbear scales pretty poorly with items. As such, you want to get items that help your team, and armor/hp for tanking turrets and diving. You have a few items that are very good on Volarbear, and which one you get is dependent of how the game is playing out.

Boots of Swiftness - Very good boots for Volarbear. Swifties are the best for gap closing, which is crucial, and the slow reduction is essential for mitigating the effects of kiting.

Wardstone - I don't think I need to explain this one.

Aegis of the Legion - Get this fast if your teams is grouping up early and taking towers. Upgrade this if the other team is heavy on magic damage.

Zeke's Herald - Get this if your team is not grouping early, and its just you and your ADC bro'ing it up for an extended period in bottom lane.

Locket of the Iron Solari - Good for diving towers, teamfights.

Ohmwrecker - Get this whenever you are ridiculously far ahead or you play against Evil Genius' EU team.

Randuin's Omen - Another good teamfight item, and a good buy if your team is lacking a strong front line or you are always the enemies' focus during fights.