OK, I'll give you my process for making drippings gravy - it'll look complicated because I'm typing everything out in beginner steps like I did for my sister 2 years ago when I got a panic call on Thanksgiving day, but it's really not hard.
1. When the turkey goes into the oven, put the neck, a quartered onion, and a few slices of celery in a small pot. Cover with water, and simmer for a couple of hours. When it's ready, remove the neck to cool; strain the broth. Shred the turkey meat off of the neck and reserve separately. Alternatively to this whole step, buy a quart of chicken broth.
2. When the turkey comes out of the oven, pour the drippings into a fat separator. If you don't have a fat separator, pour them into a glass measuring cup or deep bowl. The fat will separate into a oily-looking layer on top of the juice.
3. Once it settles, separate the fat into a different container. If you have the fat separator, this is easy. If not, just use a metal spoon to skim it off and dump it into another bowl, or stick a turkey baster deep into the bowl to suck the juice out, and transfer it to a separate bowl, leaving the fat in the original one.
5. Add enough of your broth to the "juice" part of the drippings to make 2-4 cups, depending on how much gravy you want (I like to make a LOT of gravy).
4. In a smallish pot or deep skillet, heat up about 2-4 Tb flour - one for each cup of broth. Over med/low heat, add an equal # of Tb of flour, whisk until it turns amber-colored. Slowly add the broth, whisking constantly.
5. Once it's all bubbling, turn the heat down as low as you can - you want it barely simmering. If it gets lumpy (usually from too much heat), take it off the burner and whisk like crazy until it smooths out. Add the shredded turkey meat from the neck. Simmer for at least 15-20 minutes, or until you're ready to eat - it won't hurt it to simmer for much longer than that.
6. Taste before serving. If it's too thick, add a bit more broth (or water if you're out of broth). Add salt and pepper as desired. If it's too thin, turn the heat up to medium and whisk constantly until it thickens. If you REALLY screwed up the ratios and it's still way too watery, combine 1 Tb flour and 1 Tb fat in another saucepan, heat and whisk to make a roux, whisk a cup of the gravy into the roux, then stir the whole thing back into the gravy pot.
You can also add the giblits with the neck. When you remove the neck and shred the meat from it, chop the cooked giblits into tiny pieces. Add them with the shredded meat. Or, you can skip all of the meat if you prefer a smooth gravy.