In a larage pot, over medium heat cook and stir flour and oil until caramel colored. (don't burn please) add the celery, green pepper and onion cook until tender, stir in the broth, garlic, salt, pepper and cayenne bring to a boil, reduce heat, cover and simmer low for 30 minutes. Stir in shrimp, okra, green onions and tomato, return to a boil, reduce heat cover and simmer 10 minutes or so until shrimp turn pink. stir in file powder or other ingredients(if file powder isn't used) Serve with rice under. We like lots of rice under it so I have the rice on and cooking while the gumbo is simmering. Enjoy.