All the above posts are right. There is really no right or wrong way to go when it comes to fish or corals being added first.
Coral need the amino acids that comes from the fish waste.Though the corals use it in very minute amounts. Corals also need pretty stable parameters. Just how stable depends on the spices of coral.
Fish needs ( for the basic hardy 1st fish ) are pretty basic.They can handle have some nitrates in the water, flow isn't as important, a little food and cover and their good.
My personal opinion. Add one or 2 hardy fish first.Wait a couple of weeks and keep a close eye on your parameters. After a couple of weeks, add a soft coral like Xenia or Zoathids, Paly's, stuff that generally do well in new tanks.
The key is to research what you think you may want to add.Not just it's care requirements, but where it comes from and the conditions it thrives in, in the wild.
Don't just watch the tank, study the tank. It'll let you know what it needs when it needs it.