You can add some coral anytime you want. Easier stuff will be softies, like Xenia, gsp, leathers, zoas, and such, but keep those isolated, and away from rocks you don't want them to spread on to.
I'd give it a bit of time after adding livestock for the first time as you may experience some hair algae soon. It may run over your corals... you can get lucky and not have any algae problems
Good luck
I never had any issues with hair algae at all. Just make sure you have a good cleanup crew. In my 29 biocube I have 3 hermits and started with like 8 margarita snails to help with diatoms, turbos, and a few other varieties. I run about 12 to 16 snails for my own personal taste. I typically remove coral from plugs before putting in my tank but those that I did not, and any algae I may have missed was quickly disposed of by my cleanup crew. I also didn't have any issues starting off with LPS and softies... Just do your research and maintain stable parameters.