Mid Storm Spirit

Work in progress...

The description for this guide is a work in progress, sorry :P

Introduction

A hero for the adrenaline junkies, the Storm Spirit provides arguably the best non stop movement of any hero. When equipped with a lot of items, the Storm Spirit can be seen bouncing around the battlefield, zapping his foes and quickly jumping away. Raijin relies partly on his physical attack and partly on his spells to defeat his enemies. Static Remnant is his main source of spell damage. When cast, this ability leaves a staticky copy of the Storm Spirit behind. Similar to a landmine the image will explode on contact, shocking all nearby enemies. Electric Vortex is a very powerful disabling spell, which grabs a target enemy and drags them to the Storm Spirit. A common tactic is to use Electric Vortex to pull a target into a Static Remnant image. Overload completes this combo, giving the Storm Spirit's next attack a blast of electrical energy whenever he casts a spell. However, Raijin's signature ability is definitely Ball Lightning. This teleportation spell has no cooldown and no maximum range, which means Raijin can bounce about as much as he wants, as long as he has the mana and regeneration to support the high cost of the spell. Raijin behaves much like a storm, starting out weak early on, then gathering power over the course of the game until he becomes an unstoppable force of nature.

(from playdota.com)

Raijin Thunderkeg, the Storm Spirit, is a ranged Intelligence hero who wields the elemental power of lightning. He has high mobility, strong ganking and carrying potential, and very good synergy between his hero abilities.
Static Remnant creates an immobile clone of himself that, upon contact with an enemy, shocks all enemies in a small area for damage. It has a very low cooldown, making it a good farming skill. Electric Vortex binds an enemy to himself, drawing it in slowly; at higher levels of the skill, it will always be able to pull the target into a Static Remnant. Overload further supplements this combo by harnessing the excess charge whenever Raijin casts a spell, adding it in the form of magical damage to his next attack and zapping enemies in a radius around the target. Finally, Storm Spirit's ultimate and signature skill is Ball Lightning, in which he transforms into pure energy, sacrificing his own mana to dash quickly around the map in an invulnerable state, inflicting minor damage to foes he impacts as well as giving him an Overload charge. It can be used to initiate and escape long distances with ease.
Because his ultimate disjoints enemy projectiles and has no cooldown, he can prove to be one of the most slippery foes in the game, provided that he has enough mana regeneration to sustain it and/or the enemy team does not have strong disables such as stuns and silences. However, without proper mana management, he will run out of juice very quickly and be a sitting duck. While extremely vulnerable early game before he acquires his ultimate, once he does so, if he gets a few quick kills and some mana-sustaining items, he will become an unstoppable force of nature.

(from Dota 2 wiki http://dota2.gamepedia.com/Dota_2_Wiki)

Storm Spirit is a great mid hero who scales well into the late game. With the right items and skill build, he can zip in, get a kill, and zip out before you can say 'Storm Warning.' However, incorrect item builds can totally ruin your game. I'm mediocrechicken and this is my Storm Spirit guide.

Pros / Cons

Pros

Great initiator
Amazing Ganker
Snowbally
helpful in mid and late stages of the game
extremely mobile
hard to kill
relatively high skill cap
fast farmer
good disable

Farm dependant
Mana dependant
Must come right up to the enemy to execute combo
requires skill and understanding to play
needs kills to snowball
no AoE damage, mostly single-target
vulnerable to silences

Items

Disassemble Arcane Boots to finish Bloodstone. However, you should definitely finish Perseverance before disassembling to make a soul booster. Bloodstone will take a long time to farm, and you'll need the burst mana for ganks during that time.