This is how I make my brown gravy, and it has a ton of flavor.
Remove turkey gizzards, heart, liver, etc. from the trukey. Place in a 2 to 3 quart saucepot and add water to half fill the pot. Cover and bring to a boil. Reduce heat and simmer for about an hour.
While the broth is simmering, prepare your turkey for roasting.
Add 1/2 chopped onion to your broth, and a half tsp. sage. Continue to simmer until the onion is very soft. Add more water as needed to make two cups of broth. When the onion is soft, add 1/2 tsp. of salt, and a quarter tsp. black pepper. Stir for about 5 minutes and taste. Add salt as needed until it tastes correct to you. Anhd remember, add a little at a time, stir it and re-taste. You can always add more if you need to, but if you add to much, you can't take it out.
When your broth is seasoned correctly, place in the fridge unti lthe turkey and other side-dishes are finished. When the sides and the turkey are done, heat teh broth over medium high heat until lightly boiling. While waiting for the broth to come up to temperature, heat 3 tbs. butter in a shallow frying pan. Add 1/4 cup AP-Flour to the melted butter. Stir rapidly to incorporate all of the flour into the butter. You should have a very thick paste. Add more butter if needed and stir until the flour/butter mixture flows accross the pan bottom. Cook over medium heat, stirring constantly, until the roux begins to brown. Then add 1/2 cup of broth and stir until it is incorporated into the roux. Add another 1/2 cup stir, and repeat until 1 cup of broth has been added. Then, slowly pour the thick sauce into the boiling broth while stirring. This will give you a creamy-smooth texture and great flavor. Correct the seasoning with more salt, pepper, and sage if you need to. The flour flavor will alter and dilute your original seasonings. Add any pan drippings and juices to the gravy to strengthen its flavor. Try to avoid adding the fat.
Though this text is fairly long, the method is easy and not very time consuming. And it will give you what you are seeking, and that's what cooking is all about.
Seeeeeya; Goodweed of the North