Gravy steak or gravy beef is a tough cut. It's for slow cooking and all that fat will render down to keep it moist.
I'll usually chunky dice it, brown it in a pan, throw in some veggies, a little flour to thicken the sauce as it cooks, tomato paste, red wine and a bit of water or beef stock to cover it. Cook for 4-8 hours in a slow cooker...delicious with a bit of mashed spud on a cold winter's night!
Or you can always get a slow cooker flavour sachet from the supermarket