Well there's four different active live action Earth's if Supergirl isnt on Earth 2.
Flash/Arrow Earth
Zoom/Jay Garrett Earth "2"
Supergirl TV Earth
Superman vs Batman Earth.
Assuming we're not counting earlier DC shows and movies.
Supergirl doesn't seem like it is same as movie Superman unless Man of Steel took place in the late 90s or Supergirl is in the 2030s
Definitely not. The depiction of Krypton is distinct and incompatible. And James said in the Supergirl pilot that Superman's first public act of heroism was saving a plane, which I don't think is remotely compatible with MoS.
And I have no idea where Gotham fits in.
I've started to think it's Earth-3 and that it's secretly the origin of Owlman rather than Batman.