How I like to make gravy for red meats:
After roasting whatever red meat you favour (beef, lamb), deglaze the roasting tin over the stove by adding about a glass of red wine. Leave to simmer and until the alcohol has evaporated. Then add a little cornstarch dissolved in warm water (about a dessert spoonful of cornstarch to a 1/3 of a glass of water or less) to what you have so far. At the end, add more or less cornstarch and water if you feel that the gravy has reduced too much. At the very end, stir in a few good lumps of butter. Serve!
For chicken I don't add red wine, but instead of just adding some water you could add a little cognac or some chicken stock for extra flavour. The rest of it is the same as above. Hope this helps