This is my wife's grandmother's recipe. She lived in Mobile, AL and made a great gumbo. You need to keep in mind that they made it with whatever was available seafood-wise. You just need to make a roux and add some chopped vegetables. The seafood goes in last.
You're going to need between 3/4 and 1 cup of bacon grease so if you don't save your bacon grease then go buy two or three pounds and fry it up. No point in starting until you have the grease in hand.
Here's the recipe, word for word.
Step 1: Chop and combine: 1 cup celery (3 stalks), 1 cup onion (1 large), and about 1 cup bell pepper (1 1/2 large peppers).
Step 2: Make the roux. Brown until dark 1 cup of flour and 3/4 to 1 cup bacon grease. Stir constantly!
Step 3: When brown add vegetables to the roux and cook about 5 minutes. Then add 1 can beef boullion, 2 quarts water, 1 small can tomato sauce, 2 tablespoons worcestershire sauce, 4 cloves of garlic (minced), and 4 bay leaves. Then add 1 pint of chopped okra and salt and pepper to taste. Add crab and shrimp [amount is unspecified but I would say at least 16 ounces of lump crab meat and 2 pounds of peeled and deveined shrimp].
Simmer this mixture covered for about 1 hour.
My wife normally makes a double recipe when she makes it as it's pretty good left over. I think we would normally use about 5 pounds of shrimp and a couple of pounds of crab meat for a double recipe. Getting the roux correct is the secret to gumbo. It needs to be dark but not burnt.
Edit: We often make gumbo when we are at our condo at the beach and we normally have access to live crabs. We will clean them and throw 3 or 4 cleaned, whole crabs and claws into this recipe. Also, we normally eat gumbo with a bit of tabasco on top and saltines to the side.
