In a large skillet, brown the andouille sausage and chicken over medium heat with 1 tablespoon of vegetable oil. Once browned, remove from heat and set aside.
In a large dutch oven or heavy-bottomed pot over medium heat, combine the oil and flour to create a roux. Stir constantly for about 15-20 minutes until it turns a dark, rich brown color.
Add onions, bell peppers, and celery to the pot. Season with salt and pepper. Stir frequently until the vegetables have softened, about 5 minutes.
Add the garlic, thyme, oregano, paprika, and bay leaves. Cook for another minute until fragrant.
Stir in the browned sausage and chicken, ensuring that they're well coated with the vegetable mixture. Cook for about 5-7 minutes until the chicken and sausage are heated through.
Slowly pour in the chicken stock while stirring. Add in the can of diced tomatoes with green chilies. Bring the mixture to a simmer. Reduce the heat to low, cover, and let simmer for about 1 hour, stirring occasionally.
Add the shrimp, crab meat, green onions, and parsley. Stir well, then cover and cook for about 5 more minutes until the shrimp are pink and cooked through. Adjust seasoning with salt and pepper as needed.
Serve the gumbo over cooked rice, sprinkled with a bit of filé powder, if using.