making gravy is one of those things that varies from ultimate simplicity to very complex.
"taste" more-or-less coincides with "degree of complexity" - but there is "over do"
at the ultimate simple level - cook equal parts by volume fat (butter works well....) and flour, after it's cooked (gets rid of the raw flour taste) add water. flour thickens water, bingo, you got "gravy."
things that add taste are the flavor of the fat and the other "solids" that get incorporated into the gravy.
in the good ole' days, when the turkey was done, it was removed from the porcelain roasting pan, the roasting pan went on the burner(s) for "deglazing" - if you're using a disposable aluminum foil roasting pan, this is not a good idea. scraping the pan to loosen the 'fond' will likely result in holes and a big mess on the stovetop . . .
"add flour to the drippings" - that works. unless you've deglazed the pan, just pouring out whatever is there will miss some goodies - but as mentioned, deglazing the pan entails some "conditions of a practical nature."
the liquids coming out of the roasting pan are unlikely to produce the volume of gravy needed.
because the volume of fat/water/fond extracted from the roasting pan is a bit unpredictable, here's my madness approach:
for each person I plan on half a cup of gravy (4 fluid ounces) and I plan in 50% extra for gravy fans and leftovers - so my "finished" goal is 6 fl oz of gravy per person.
for example if you're serving mashed potatoes with puddles of gravy, double the 4 ounce + extra theory....
in advance:
prepare 4 tbsp flour with 4 tbsp butter roux, cooked to a blond stage, cool, refrigerate
(that's a safe planning quantity for 2 quarts of gravy)
procure multiple cans of chicken stock (okay, okay, chicken ain't turkey, but it's close)
procure dried mushrooms - if you hate mushrooms, omit this step
procure leeks / scallions - if you hate onions, omit this step
if you like giblet gravy, boil/cook/braise/stew & dice the giblets. save/refrigerate them in their own juices.
(use a minimum of water when cooking the giblets)
if you hate giblets, omit this step
bring one can of chicken stock to a simmer, add finely diced onion, dried mushroom, remove from heat, allow to "steep" for 20-30 minutes.
remove the biggie dried mushroom chunks and dice finely.
on 'the Day'
at this point, the turkey is cooked and resting.
deglaze the pan, if that's possible, put results in a sauce pan, add low heat
add the onion/mushroom/giblet components and allow to reach simmer
add chunks of the roux to establish a basic consistency
add roux/chicken stock to achieve the desired volume & thickness
test taste for salt & pepper
always "think thinner" in the sauce pan, gravy thickens as it cools.