When you do add corals, be sure you place them very low in the tank or in a shaded area for the first few days or even a week. That will allow them to acclimate from whatever tank they came from to your's. Light shock can cause bleaching in many corals. Once the short time has passed, you can then move them upwards a few inch's every few days until they are in the desired location.
I would suggest leaving shrooms
near the bottom. LPS
corals like brains and plates should remain on the substrate. Softies should do well no matter where they are placed after acclimated to the light. I would however hold off on any SPS
or clams for another 4-6 months though. They do not tend to do well in newer set ups.