Get everything in. Sand, LR, water (put sand in, cover w/piece of plastic, add water to about 3/4 full, then add LR and get your aquascape in order. Get all the pumps on, etc. Let it all settle in for a day or two. Then add your cleanup crew. After everything is kinda stable (assuming the LR you added was cured), this should be quick. Once everything is nice and comfy, water tests well, temperature and PH is stable, then add your chromis.
Next, just chill out and let everything settle in for a few weeks. Do a water change, then start planning your next inhabitants. I would keep it simple till the tanks is 6 or more months old. I'd stick with the rule of not adding more than 1 fish a month.
Good luck!