I need an authentic bauhaus typeface, which to use? Preferably one from around 1930 if possible.
Could you help me?
FF Bau (aka "Scheltersche Grotesk")
P22 Bayer Universal
You might also want to take a look at this brand new font family:http://www.fountaintype.com/typefaces/dessau
Take a look at P22 Bayer Universal, designed by Herbert Bayer himself. It's more authentically Bauhaus than Benguiat's later Bauhaus creation. 17 similar fonts.
j a m e s
And for a geometric design from 1930 this typeface originally drawn by Jan Tschichold (not a real Bauhaus designer though):
The Foundry has special collections connected to that timehttp://www.foundrytypes.co.uk/
Architype Collection 1 and 2 might work for you
LTC Twentieth Century Pro (which is essentially Futura) includes the Paul Renner designed geometric alternates.
... but Renner has never been part of the Bauhaus...