janna

I would just stick with mobility boots. I don't think she's a viable mid laner! Not enough damage.

Late game, getting an AP Support item can get you both movement speed and some ability power. I usually build her AP Support

As for Mid Lane and Sorcs, I don't really see her doing damage, even if she were to go full ap in the midlane. Mid Janna always felt like a 'Control Mage' to me. Able to shield and heal massive amounts while disrupting teamfights and dealing some slight damage. Luden's Echo with a Lich Bane could slightly remedy her low damage output, though.

she is just when it becomes a mage meta like when that comes never

Here is how I look at ap janna wow o wow is it strong but let me correct you on something ap janna is not really there for dmg (although her w chunks) she is there because her shield becomes crazy when you can shield someone for 300 health and give 80 attack damage and when here ult is stronger than the actual base (besides the mana regen) long story short when you go ap janna don't go sorc boots adding on to this don't run ms quints take the ap quints and for your janna mid question well doesn't seem too strong because of the lack of dmg but I'm sure it could work