Gravy base: one part fat to one part flour. E.g., for every tbsn of turkey fat/vegetable oil/butter/whatever fat floats your boat, add 1tbsn flour. The liquid is about a cup for every tbsn of flour. You can use water, broth, wine, whatever. I use mostly turkey broth, with a little hard cider.
So, heat fat to sizzling, dump in your flour, whisk until you get good color. You are making a roux. It takes a long time to start coloring but it goes dark very fast once it starts to darken. I aim for a copper color. Once I get that I toss a few cups of broth in - not all the broth, just enough to stop the flour from cooking- and whisk madly. This works the lumps out. I gradually add enough broth, still whisking, until I have a very very thick mass of gravy. At that point I take it off the heat and I leave it until dinner is almost ready. You can even do this the day before and put in the fridge.
Right before serving, I bring the gravy back to heat, whisk in the remaining broth and and pan juices (not fats) to get the thick/thinness I want, then add a touch of cream.
Ps...use a big enough pan. Seriously. Don't try to do this in a tiny pan or you will never succeed. That's the biggest mistake I see people make.