Below is the list I made for myself when I was preparing for my tank build. I added some notes since many things are not required but will make things much easier.
Tank
Lights
Powerheads
Sump - Not required but recommended.
Protein Skimmer
Return Pump - Not required if not using a sump.
RO/DI Unit - Not required if you buy RO/DI water.
Controller - Not required but a huge help.
Auto Top Off - Not required but a huge help.
Dosing Pump - Not necessary at initial start up, and may not be necessary at all depending on what coral you keep.
Chiller - May not be necessary depending on the temperature in your home.
Heater