Originally Posted by forty_caliber
Assuming everyone gets 2 biscuits I would guess 6 oz of gravy. Understand that this may be a TEXAS portion. The key is determining the serving size per person.
30 x 6 oz = 180 fl oz
or 5.625 quarts.
Figuring a quarter pound of raw sausage per person, for thirty cups of gravy, you will need 7 and a half lbs. sausage, and the same amount of flour. This works out to about two tbs. flour per person, which should give your sufficient roux to make the required amount of gravy. You might want to check my math. I did it in my head, and as we all know, my head isn't always all that accurate.
That's why I use recipes as a starting point.
If it were me, I'd cook up the sausage and start adding flour, a little at a time, until the roux was thick enough, and slowly whisk in the milk until the gravy was just right. After that, I'd add salt and pepper in the same way, testing after each addition until the seasoning was right.
Seeeeeya; Goodweed of the North