Easy soft corals and hardy stony corals are easier to begin with in my opinion. You can add them to newer completely cycled systems and not have to worry about over loading the evolving biological filter. No feeding, no quarantine required. The longer you wait to add fish initially the better. Once you start to see the initial algae blooms and the cycle has ended start with a few members of the clean up crew, you can feed them sparingly this also feeds the denitrifying bacteria.