Please people, read the entire guide before voting. If you have any comments, go right ahead :)
No let me start off by saying this is not your average troll build. It is not meant to be a complete and utter jerk to your team mates. In fact, you may find yourself saving the lives of your allies many, many times. Sure, in a team fight you may not be much use aside from your q's knock up and MAYBE your ulti's heal/knockback. And in a fair fight, you would be completely demolished by any competent player. Not to mention the fact that if you get cc'd, you'll most likely get burst into smitherines...
But who cares when you can run insanely fast!? :D
Your utility will be off the charts, you can distract their entire team as they waste precious time trying to kill you, and not to mention how hilarious it is to kite with her.

All the items in this build are for the run speed. Zephyr is probably the most core item of all, as not only does it give you run speed, but it also reduces the effects of all CC! And CC is the bane of all speedy characters. Can't exactly run away while you're snared can you...
A good point to mention is that although your trolling, you dont want to just have fun suiciding. Your goal is to sprint around the map tormenting your enemies, and testing how good you can get out of the stickiest of situations through smart use of ALL your skills. Do you have the foresight to place down a q in a bush during your escape to surprise knockup any chasers? Do you have the wisdom to decide when it's smart to get close enough to slow? Are you fast enough to shield yourself and your allies right before they die? Are you hilarious enough to Ulti your enemies straight into your team through a strange anti gank? This build will test all these unbelievably funny troll techniques.

Now why did I choose the runes I did? Because simply, it helps with trolling :) And isnt that what this guide is about?
The glyphs are CDR per level, because its the only place you can get them. Seals and Marks are Flat CDR because who doesnt wanna start the Q pam straight off the bat? Your quints on the other hand, should 100% be movement speed. Run, run and more running is the key point of any successful janna troll. Can't touch what can run 3x as fast as you ;)

Well this is interesting...
Do you want to be good troll janna? Or Diabolical troll Janna? First off, let's find out what the diabolical troll janna entails...

EVIL JANNA TROLL OF DOOM

In team fights, you use your ulti to save your enemies/help them catch up to your team
You shield yourself, and yourself only
Q to save an ally? Don't make me laugh...
Dropping wards in the enemy base? YES PLEASE!
Flying at full speed with Shurelya's active into the enemies LAZORRRR is IMPERITIVE to your team's success
Don't forget to go into any lane other than the one you're supposed to be in :)

"But I don't want to be a jerkish troll! D:" I hear you say (lol jokes, no troll says that ;) But here it is anyway...)

GOOD TROLL JANNA :)

Use your ulti to help your allies escape, heal them up in a team fight and push a stupid enemy team into your turrets
Stay at the back of your team flinging q's in everynow and then
Watch out for your carry especially, and shield him whenever a fight breaks out. Without any AP built, it will be pathetically weak... But somethings better than nothing right?
For the love of god, stay in bot. Don't steal farm, kite your enemies with your insane speed and drop a Q every now and then.
Early game harrasing? Hide in bush as much as you physically can. Pop out autoattack and retreat back in. You don't want them to have a chance to fight back... With your superior speed it should be easy
BAIT BAIT BAIT! Bait those suckers in attempting to kill you (like that's possible... ;)) and surprise them with your entire team waiting around the corner
When your team inevitabley loses every team fight (You're effectively the most useless person ever) Throw your q behind your retreating and proc it at the last minute so you get the maximum knock up time :) You will give them some much needed escape time.
Use your Q and proc it immediately the second you see someone using any sort of channel ulti, your team will appreciate it :)
Use your W to help your carry confirm kills
Run into the enemy teams base LAZORRRR ;) It will boost your teams morale! :D (Jokes they will hate you...)

As you can see, being a good troll Janna is MUCH harder than it looks. So don't judge a troll straight away, they may just be trying to have a fun time using an alternative route :)