whos the best AP champion for mid?

depends on ur playstyle
can be brand can be anivia can be anything....

Leblanc , cuz shes madness early game , 3 hit instant kill at lvl 6

It's personal preference....... My favourite ap mid champion is LeBlanc but that's just my opinion, as I said there's no 'best mid champion', it's personal preference.

depends on who you are fighting...

Leblanc is not playstyle dependant because shes totally unviable late game her early is her only keypoint mid and late shes no good. I would go for malz/brand/anivia for best mids atm. But just play what you like best for mid.

Garen

I would go for Le blanc or Morgana. But it really depends on who you're against

There is no "best" really as they have different playstyles which will best suit different players.

In general though brand is probably the strongest AoE AP and annie the strongest burst AP with morgana as the best AP counter/support. Ofcourse this doesnt make the others any less viable, Cassi is my personal favourite.

I like akali... trolololo