A few other thoughts as another son born and raised in LA, listen to what he says about NOT burning the roux! Roux mix ~0.75 cents can ruin an expensive seafood or any other gumbo. Some like to skip the roux - well it just aint the same. I'll fess up to liking the slow cooked roux better and more a 1 to 1 ratio, but that's gumbo, they are all a bit different.
The holy trinity "mandatory" (bell pepper, celery, and onion) - can't remember too meals as a kid that didn't contain the holy trinity
On the okra, it can make the gumbo a bit slimey. If that's not to your liking consider file powder as an option. I do recommend you taste and watch the file portion if it's new to you. It has a very destinctive taste and also acts as a thickening agent.
Now I think I'll make some seafood gumbo this weekend. Great thread!