You will need a compressor that can provide a nice steady flow of dry air around 80 to 100psi. The volume isn't so important as the CFM which will depend on how you run the spindle regards the Air seal and how often you change tools.?

For instance, if you don't use the air seal option which some people don't because it uses lots of air and also blows dust around then your CFM requirements will be a lot lower as you only need short blasts of air for the drawbar and taper cleaning, and you only need it when changing tool so the compressor has lots of time to refill the tank before the next tool change so can get away with smaller CFM rating. Also, if you have a larger tank then you may get 2 or 3 tool changes before the pressure drops enough for the pump to fire back up.

However, If you use the air seal then you will need a compressor with a high CFM so it can replace the air you are constantly drawing while the spindle is running. This is why the air seals are often left off as they eat air which means the compressor is constantly on/off, esp if run with a small CFM pump.

I would look for a compressor around the 14-15CFM area and 200ltr, smaller than this and you'll find it's constantly on/off if using the Air seal.