I don't like your runes, I prefer taking all mana regen seals, because CDR you get from those runes is practically non existent, therefore not worth it. Glyphs give more CDR, but since u pick AP glyphs I would prefer taking AP/lvl glyphs because early game u don't need that much AP for Janna as your main focus is to support and at low lvl it doesnt help all that much. also you'll be getting AP items quite late so if u wanna stack it, i think those runes are better.
Also I dont asee why u should take mag pen quint, janna is a support, not needed to deal damage. Other than that I have nothing to say about runes, but something about your summoner spells...

wouldnt VC be better? Exhaust is better for carries. And i dont see why u should take Rylai, because jannas attack spells already disable the team, she has slow and howling gale pretty much covers up for it by knocking enemies into air. I know it gives HP and AP but other than that it's really expensive for a support.

I hope my comment was of help to you :)

nice build, good work ill give it a try =)

Okay. Building AAS is cool. But, if you're making it a last item, then grab Tear of the Goddess earlier. It's a great earlygame item, and if you get it as late as you do, it's :/

Thanks, I'll try to work harder on this build and make it more perfect. It should be updated soon.

I could do with more analysis on skills and items. Other than that +1