Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
First off, this build is brought to you by Thantis, so entirely credits to him. Mostly up for my reference, but hopefully you guys can find a use for it.
Masteries: 9/0/21. On someone like Janna, you don't need the Defense. And Utility is obviously important for supports.
Summoner Spells: Clairvoyance because it's amazing especially on supports. Flash because Janna has no escape mechanisms. Sorry folks who wanted Teleport, Janna has plenty of movespeed.
Runes: I chose armor reds simply because Janna doesn't need the magic pen that much. She has Archaic Knowledge anyway. Don't like it because they're secondary? Time for you to read up on runes. MP5/lvl yellows obviously because they're pretty much the best Seals in the game on anyone except manaless champs. CDR blues, pretty universal and great for Janna. And if you're complaining about flat health quints go see a psychologist.
Skills: SKILLS ARE SITUATIONAL! Do not immediately put your first point into HG. If you think you need your shield, go with that first. Same goes for what to max. If you have a strong dps in your lane, max shield. If you need to poke and farm, max HG first. Always max Zephyr Last but take a point in it at 4. And obviously ult at 6, 11, 16.
Items: Pretty much universal, nothing situational with a few exceptions. In terms of boots, I find that Ninja Tabi is almost NEVER worth it on Janna - if you're getting focused that hard that you need them, 12% dodge isn't doing **** for you. Also, for the 6th item you can either go with Guardian Angel or Rylai's Crystal Scepter, depending on if you're doing well or not. Oh and one last thing: obviously supports suck at farming, so if you can't get Soul Shroud by midgame, get Aegis. Aegis is ONLY good midgame - it's **** early and late game.
Hope you enjoy the build :D