I'm sure others will come up with better recipes than what I usually do (mine is done to taste, sorry, no exact measurements) but I just wanted to add my two cents worth . . .
Start with a really good sausage. I think this is key for the flavor of your gravy.
Personally I like the sage flavored (Jimmy Dean's is pretty good) but others like more of a peppery sausage. I would stick with a mild and stay away from hot sausage.
My recipe is pretty standard (I think)
Brown the sausage till thoroughly cooked. Here's another "key" -- Drain some of the grease as you cook the sausage into a bowl and set aside (you should have a good 6tbs+ of grease, or more, depending on how much gravy you make.) Don't overcook your grease. Burnt grease makes burnt gravy. Once the sausage is done to your liking, remove from pan and set aside.
I like my sausage well done, so at this point I drain the well-done grease.
Return the pan to a high fire, add your grease 'till hot. Sprinkle in a few tablespoons of flour and make a roux. Stir constantly! until the flour and grease are well incorporated it should be pasty with no lumps.
Slowly add milk, a little at a time (start with 1/4 cup or so) incorporating it into the roux mixture, stirring constantly
-- when there are no lumps, add more milk (you can add more and more milk each time as the roux thins, just make sure to stir out all lumps before adding more) Repeat until the gravy is a little bit thinner than you think it should be when served.
At this point add any spices (I usually just do salt an pepper.)
Once you're at this stage, rest your stirring arm
and let the gravy come to a boil. In the mean time, crumble the sausage (I like lots-o-sausage. Just add what you feel is right.)
After the gravy has been to a full boil for about 2-3 minutes (flour will not thicken until boiled) stir well and lower the heat to a slow simmer. Add the sausage and let simmer for about 5-7 minutes (to cook out the flour taste) taste and adjust seasoning . . . and you're ready to serve!
For biscuits, I usually use the Pillsbury or Poppin' Fresh biscuits in a roll. (whenever I tried home made, they came out dry and crumbly.
Serve with the extra sausage on the side.
Sorry if I got too much into "gravy-making 101" but it's not always just the ingredients that make a good gravy.