is avogadro's law for the same gas?
Since Avogadro's Law is speaking about ideal gases then it's true for all gases that behave ideal.
Since ideal gases don't interact with each other and don't have any volume for single molecules (they only have a volume as a whole) Avogadro's Law holds for different gases.

Since for real gases the approximations of the ideal gas don't hold then Avogadro's Law doesn't hold. Yet a ratio similar can be achieved by dividing V over n of different gases to get the molar Volume and by using different equtions to describe real gases a ratio factor can be achieved for a given pressure and temperature.