It depends on these factors and maybe more.
Tank size
Obviously, larger tank=more room for the fish to be more social distancing.

And to make the below factors work.
Aquascape
Often overlooked but rockwork is everything. Too much and the fish will have no where to swim without hitting each other. Remember, fish have these sensories that detect objects so that they don't hit it. Ever wonder why your fish don't just bang into the glass? The more obstructions they have to avoid, the more prone they are to sensory overload. This increases stress and anger issues.
Too little rocks and the fish will have no place to go tuck themselves overnight. This will create a lot of torn up fins and injuries. Ever watch your fish when the light starts to dim? They all try to find themselves a nice crevice to go into. And any intruder of your space will be aggressively attacked.
Introduction of Fish
My method has been plan out your fish species and add them all the same species together at once.
Fish size
This is more important for Tangs. Find out what is the most agressive and least agressive. IME. Yellow tangs or Zebrasoma species are the least troublesome. The Acanthurus is what you have to worry about. Get them small but keep in mind that a Powder Blue is very agressive and will beat down a larger Powder Brown.
Have a tang to rule them all.
Use an acclimation box
If you must add in a new fish that is the same species as an existing fish, use an acclimation box. Get the fish to eat comfortably and other fish acquainted. Nothing worst than adding a new fish and it's being chased down and pecked on while it's trying to be accustomed to the new environment.
Feed, feed, feed.
I don't need to elaborate this. Just watch the Snickers commercials.
Again, make sure you know what you have in terms of water volume, filtration capability, and the fish you want to keep. And prepare to remove dead fish. There's no method that will be 100% successful. Just try your best.