Not Updated For Current Season
JUST REMEMBER, JANNA TAKES ALOT OF SKILL TO REALLY PLAY WELL WITH HER AND WITH THIS BUILD, YOU BETTER KNOW HER WELL OR YOU WILL THINK ITS ****! BUT TRUST ME, WITH PRACTICE, YOU WILL LOVE IT.
I play DPS/Nuke Janna and I ALWAYS solo mid (5x5) when playing with my team. Janna is really REALLY effective levels 1-12 and she sets the tempo for the match. She can pretty much hold her own at mid against any champion. I harrass all day and most of the time get first blood. I always go shield, zephyr, howling gale, then rotate shield and zephyr till maxed out. I usually don't need my ult till later in the game so I do not put a point in it unless I need to. Early game my main concern is harrassing and using HG to multiple kill minions. Remember not to spam HG to much because you will notice "OMG I HAVE NO MANA!" real quick.
For items, I always start with meki pendant and 2 HPs and Heal and Clarity for my spells. I usually try to lane until I got around 2000gold then go back for Besearker Greaves and Zeal. From there I get Last Whisper, Then Nashors Tooth, and usually end the game with Phantom Dancer and BF Sword (I 30% of the time get BF Sword but matches dont usually last that long).
The main thing about Janna is EARLY GAME, you need to push mid and harrass HARRASS and HARRASS more.
For runes, I go all attack speed(SEAL AND MARK) and ability power(GLYPH). I have tried alot of different rune setups and with this build have found this to be the best with the exception of switching out AP for mana regen in glyph.
Let me know whatcha think and try not to hate to much.