I am a janna main from NA. IGN: coalcrunch. I have been playing janna since I started playing back in season 4. I got plat in season 6 but I was playing with diamonds and higher as well. Im trying to get masters with this build this season. Good Luck in solo queue bois.

READ ME:
PSA: Please don't type in the chat. ever. Nothing ever goes well if you type in the chat. The only thing I will ever type is "gj" when we make a good play or whatever. If you follow this rule you will, without a doubt, gain lp because of it. After I stopped looking/ using chat I tilted less and won more.

Janna is a defensive support so it is better to pick a defensive summoner spell like exhaust. You could probably pick ignite in certain match ups but I would take exhaust mostly.

I build eye of the watchers because it allows you to have a purpose in the lane other then just shielding your adc. You want to auto or w the enemy laners when ever they step up to close to farm for example. If your doing well you can get a mejais soulstealer. This is very easy to stack because of the assists you will be getting. Your items don't really matter after you complete your death cap. Just get whatever you want afterwards.

Why I don't go redemption (or meta build, i.e. coin, sightstone, redemption, mobos).
I dont go redemption on janna because I personally don't like using the item. I think the delay on your cdr and 2 minute cooldown adds up to just not worth the value you get from your ardent censor.

In fights you gonna wanna shield who ever your main damage dealer is. Primarily your adc. Also work on misplacing champions that have gap closers with your q or ult. Start off using your ult while they are moving. After you master using your ult, then move on to using your q. Using your ult for this purpose is easier to time because you don't have to charge it up. Remember your only job is to keep your damage dealer alive. The easiest champions to knockup are zac, lee sin, leona, thresh.