Make the Broth: Heat oil in large saucepan over medium-high heat. Brown turkey giblets and neck for 5 minutes. Cook onion for 3 minutes. Cover and cook over low heat for 20 minutes.
Add chicken broth and water, scrape pan bottom, and bring to boil. Add herbs and simmer, skimming foam from surface, for 30 minutes.
Pour broth through fine-mesh strainer. Reserve and dice heart and gizzard. Refrigerate broth and diced giblets until ready to use.
Make the Roux and Thicken the Broth: Melt butter in large saucepan over medium-low heat. Whisk in flour. Cook, stirring constantly, until nutty brown and fragrant, 10 to 15 minutes. Bring reserved turkey broth to simmer.
Gradually add hot turkey broth to roux. Vigorous and constant whisking at this point is key to avoiding lumps. Reserve 1 cup of broth for deglazing roasting pan (see #9).
Simmer gravy, stirring occasionally and skimming scum from surface with spoon, until thickened, about 30 minutes. Set aside, covered, until turkey is done.
Deglaze the Pan and Add the Drippings To the Gravy: Pour drippings through mesh strainer set over measuring cup. Let liquid settle until fat rises to top. Return vegetables in strainer to roasting pan.
Tilt measuring cup and use wide, shallow soup spoon to skim fat off surface. Reserve defatted drippings. Return gravy in saucepan to simmer.
Place roasting pan over two burners at medium-high heat. Add wine and reserved 1 cup broth and scrape up browned bits in pan. Boil until liquid reduces by half, 5 minutes.
Strain roasting pan liquid into gravy, pressing on solids to extract all liquid. Add defatted drippings to taste. Stir in giblets and serve.