Lightly saute onion, celery, and peppers in a large stockpot using just a splash of oil and a small splash of water.
As you are doing that, brown your chicken and sausage with 1/4 cup oil in a large skillet (it's okay to do brown the meats separately if all the meat wont fit into your skillet at one time)-- just save the greasy leavings when you finish as you will use it later to make your roux.
Once meat is browned (I actually brown my chicken breasts whole and THEN cut them into bite-sized pieces as the chicken is harder to cut when it's raw; but with the sausage I go ahead and slice it up first before browning -- ) add meat to the stockpot with the sauteed veggies.
Add the okra, tomatoes, tomato sauce, and all spices.
Lastly, add the roux. (You make the roux by stirring 2-3 tablespoons of flour into the hot oil left over from browning your meats. Keep stirring as you add the flour and cook it into a golden paste. Only takes a couple of minutes to make).
Let your gumbo cook on low for a good couple of hours. The longer it cooks, the more enhanced the flavor.