@addicted-to-smoke A) Short boil, then simmer the neck & gizzards, w/herbs of choice for some stock.....
B) The bird itself loses "x" amount, so keep those as contained as possible......I do this....
....turk in pan, celery crossways under so it doesn't stick to the pan,.maximum extension of said "bird juice" by loading the pan w/ chicken broth.....
I keep the pan pretty full during the first part of the cook & let it boil down & concentrate near the end.....
Chicken broth (unsalted) will not change the flavor in any noticeable way,; it's fairly neutral, actually.....
Doing both those things will generate enough base for about two gallons of gravy & whatever you need to dump over the carved pieces....
Here's the wife's pot for stuffing flavoring going right now...
Here's the gravy stockpot, right now....
notice the size difference.....