Begin by getting your chicken cooking. I like to make mine in my Instant Pot so I can be hands-free to cook the rest of the gumbo. You can find instructions here. You can also bake your chicken breasts on a nonstick cookie sheet (or use a nonstick mat) in the oven at 350 - 375° F for about 20 - 25 minutes with olive oil, salt, pepper, and some Tony's Creole Seasoning on them.
While cooking your chicken, you can also cook your okra. Baking the okra ahead of time will keep it from getting stringy and slimy when you add it to your gumbo. It requires 15 - 20 minutes to cook, so I usually pop it in the oven at 350° F when I throw the chicken in the Instant Pot and start cutting up veggies. Check on it once or twice and stir to be sure it is not burning.
Cut up all your vegetables. I separate them into groups because I find it easier to just toss them into bowls by what goes in the pot when. Combine your diced onion, celery, and green pepper. In a separate bowl, combine green onions and garlic.
Begin your roux. It will take a few minutes to heat up but will start to change quickly once it has heated up. The colors will change from white, to light brown, and then the perfect shade of brown - somewhere between sand and a cardboard box.
Add your first group of vegetables (Group #1) and cook for about five (5) minutes.
After the onions start to appear translucent, add the second group of vegetables (Group #2) with the spices and your can of tomatoes, and your shredded chicken.
Cook for another five (5) minutes and then add your chicken stock, water, more salt, & pepper. Bring to a boil.
While the gumbo is coming to a boil, cook your andouille. I like to use quartered pieces of sausage - you can also cut it into rounds.
Add the cooked andouille to your gumbo once it is boiling and reduce heat to a simmer. Simmer on low heat for at least an hour, I recommend 3 hours. Gumbo gets better the longer it cooks and even better the longer it sits.
When I am working from home, I will make it in the morning and let it simmer on low, low heat all day.