So many people see Janna as just a support. You complain that her skills do not hit hard and the only skill that hits hard is very easy to miss. You may look at this guide and say, this Janna is like paper! She will die very easily! But it is quite incorrect, with a high AP, your shield can easily block 800++ damage and with the spell vamp, one minion wave will give you tons of health! Now why did I name this guide Offensive and Supportive? You notice that all of Janna's skills supports in a way, knocking airbourne, knocking back, slowing, shielding, increasing damage, protecting towers. So lets cut this boring talk and go to the rune selection, masteries and items to get! *When I say turret, I mean Tower* I call it both, so just in case you have no idea wat i mean by turret, it means tower XD

Very simply... magic penetration and ability power, you want to blow the enemy away don't you?

I go 9/0/21. 9 in offense for the CDR and AP and Magic penetration. You want to have mana and threat to the opponent don't you? :D

THIS IS VERY IMPORTANT I get Meki Pendant first for the nice mana regen. Hp potions are not needed if you play like how I play(I'll explain later) But if you feel uneasy, go ahead for HP potions, they won't do anything bad to you XD If you are having a lot of mana issues in your lane, get tear of the goddess first, if nothing is bothering you much, get boots of speed. Get your sorcerer's boots AFTER you get your tear. The tear is veryvery important! *THIS PART IS THE MOSTMOST IMPORTANT PART* After getting your sorcerer's boots and tear, keep farming money(you have to hit the creep spellcasters once each and blast them with your tornado), DO NOT i repear DO NOT buy anything else until you have a good 1600gold ^.^ go get your needlessly large rod. When you get this, you are now able to KO caster minions with one fully charged tornado. This is very important as now you can set a tornado, proceed to another lane, set another proceed to another and farm money very easily. This helps A LOT in the long run. Rush for Rabadon's Deathcap next, this will instantly boost your AP like mad. You should have no problem getting Rabadon with your tornadoes all around the map. After getting the deathcap, get the Archangel ASAP. This will boost your AP sky high with Rabadon. After getting these items, you will see yourself going back to your base quite often from enemies trying to kill you when you are farming gold peacefully, so get the revolver, DO NOT do this:'Farm, get 435, go back to base buy amplifying tome, farm and do this over and over again.' By now you should realise you get your money VERY FAST. you can easily wipe out a whole wave of minions in one whirlwind! Proceed to base when you have 1200, unless you are left with 100 hp... use your common sense please. Buy hextech revolver. Now you should be able to farm VERY well. Buy Will of the ancients, finish off with Zhonya's Hourglass... use its active for your shield's cooldown!! XD its awesome to see your your enemies' faces when they thought they could kill you and you gain a sudden approx. 1k hp XD

You should always add the Q when you can unless you can add R. At lv2 add one point to W, just one point will do as you only want the slow and no unit collision. The little boost on speed is nice too. From lv3 onwards, add ulti when you can, if not add Q, if Q is maxed out, add E, lastly is W. Reasons are simple, Q is IMPORTANT, this is your bread and butter and oxygen and water!!! You use this ALL THE TIME! To clear creeps, to harass, to escape, to kill(or to help your team kill by knocking enemies in the air). R is self-explanatory, E is your turret protector and tower destroyer and survivability tool~! The increase in damage helps you destroy turrets, the shield can be cast on your turrets(YEA THIS ROCKS) and it helps you live longer(obvious, cause its a shield). XD

***GET TELEPORT*** It helps you earn money fast! you get back to base buy the items, tele back and earn more money!!!! Also, you can use this to save turrets that is about to be attacked by teleporting and shielding, while doing that, you can cast your Q adn earn MONEY LIKE NEVER BEFORE! XD The other spell depends on you. I like flash, with all my spells, I can make a clean escape using flash, Q, W, E, and R.

Always stay behind the front lines, you are squishy and you know that. Let me explain on Q, on early levels, use this(and your normal attack) to last hit creeps, if you hit an enemy hero, its a bonus harassment. Your main aim should be last hitting creeps. Once you get your Sorcerer's Boots and Tear, hit minion casters once each and use the tornado(let it charge up fully) Once you get your needlessly large rod, you can cast your tornado(not too far back, 'cause you won't hit them XD' or near, if near, creeps may walk pass it) and walk(fly) to another lane and cast your tornado again. Let the tornado charge up to its max and UNLEASH THE FURY on its own. Do not toggle it when it is charging halfway or it will not kill the minions. Always keep an eye on your minimap, there are always times when you see your opponent minions gathering and going to whack your turret hard, BEFORE they come near to your tower, either teleport and tornado OR walk(float) there if you can make it before the minions attack your turret. In mid/late game, do not go too far into enemy territory just to get your money, protecting your towers are one of your main jobs :D
When saving someone/yourself, you can use this skill and immediately fire it(your main point is not to damage, just to drag a second or so to save your ally)*note-the distance is decreased as it is not charged up fully*

-Use the shield once minions attack your tower, protecting its health is very important!
-When pushing, if you are alone with no teammates, use the shield to add extra damage to kill towers. If you have a teammate, and thier attack speed is higher, shield them instead.
-Obviously use it to save yourself or an ally from death.

-At late game, your air elemental hits VERY HARD, use it to kill/slow
-When running from ONE person, use this to slow that guy down, when running from MORE THAN ONE people, don't use this. The extra speed it grants is better.

Thats about all. Hope you become a rich Janna with this guide and I hope it helped! :D You can ask me questions, I'll try my best to answer. Thanks for reading my guide(remember to rate it!)