Meat juices, water, 100 mls or so of white wine (or red if I need a dark gravy), a drizzle of soy sauce, a tsp or so of balsamic vinegar. I reduce the gravy until it’s shiny and unctuous - the balsamic vinegar adds the sugar necessary to make that happen, This is usually enough to make a good gravy for a roast, but if I’m frying the meat I do it in Normandy butter, which doesn’t burn, but goes a lovely nutty brown, so the resulting gravy has even more flavour. I do occasionally add a spot of cornflour, and a stockpot or som Marigold to gravy but only if the meat is very lean with watery juices - all the flavour is in the fat, which also helps with the thickening process.