When I make homemade chicken gravy, after frying the chicken, I drain most of the fat off and add flour or cornstarch to the drippings and make a roux. You want it to be a golden brown. I pour as much milk as I need to make the gravy and use a wisk and stir and bring it up to a good rolling bubble (not boil) then turn it down to a simmer but still keep an eye on it. it is usually the last thing that goes on the table. As far as the chicken and noodles go, you may have too much stock or water on it. Just use milk or cream to your flour or cornstarch (equal parts). When you add the slurry that has thickened and then put it into more liquid, it has no choice but to thin.