If you aren't going to quarantine I would strongly recommend that you put in some time now learning about common fish diseases. Your fish are going to get sick, if you at least know the basic symptoms and treatments beforehand you will be in a much better position when that happens. Otherwise it is pretty much guaranteed that you'll be posting "why did all my fish die last night???'!?" in the next few months.
SW tanks are a delicate balance. One of the best things you can do is minimize stress and keep them fat so their natural immunity is strong. That means not overstocking the tank and not putting together fish that are evolved to be predator and prey for each other, or compete for resources. That'll require some research on stocking the tank. Again, with a domino damsel established in there the fish you can realistically add are minimal (if any).
If I were you I'd be feeling defensive, like people are lecturing etc. but it's really just that we want to see you enjoy the hobby. It's not that complicated, or expensive, if you learn how it works. A loooooot of folks take shortcuts, wing it, try to push the boundaries of basic care for tanks, and hope they get lucky; they are the ones that quit after a few months and tell everyone that the hobby is stupid and hard. We are just trying to help you not be that guy <3