In a large skillet on medium heat brown the sausage on both sides.
In that same pan add 3 tbsp of oil, minced garlic, and sautee the onions, celery, and green pepper.
In a heavy dutch oven on medium heat, add in the oil and flour. Mix until smooth.
Cut the heat down and cook the roux until it's a milk chocolate color. Take it off the heat. If you think the roux is about to burn take it off the heat before it does.
Add the onions, celery, green peppers, and minced garlic into the roux. Mix until fully combined.
Add in the 2 boxes of chicken broth, creole seasoning, salt, garlic powder, and onion powder. Bring to a boil then decrease the heat to a low medium.
Add in the sausage and allow the gumbo to simmer for 1 hour. Stir occasionally.
After 1 hour add in the parsley and stir. Save a small portion for plating. Taste and add in anymore seasoning if needed.
Add in the shrimp and crab legs and allow it to cook for 5-7 minutes. Serve with rice and top with parsley if desired.