You get free boots at 10 min. but you cannot buy boots before then. These boots give additional MS. For each takedown you acquire the boots 30s sooner.
Summon Aery makes Janna's [E] an incredibly strong and reliable shield.
WhyManaflow Band
Manaflow Band acts as our primary source of mana sustain in lane, allowing you to spam abilities more often for trades.
WhyCelerity
Janna is all about getting around the map quickly with her passive and [W]. Celerity empowers both of those.
WhyScorch
Scorch on Janna allows you to provide reasonable lane poke pressure with [W] harassment.
WhyMagical Footwear
Magical Footwear is a fantastic choice on many support champions as it empowers your ability to quickly get to your first important item completion and more Control Wards.
WhyCosmic Insight
Cosmic Insight is a strong rune choice n enchanter support as the added CDR means a lot more utility in teamfights.