I would aquascape first, then order more rocks later. That looks like a ton of rocks, and once you have it organized you may be able to fill in the tank nicely with what you have.
I would just always try to minimize the amount of rock you have touching the sand bed to prevent dead spots.
Pic didn't work btw (though it may be one of the image providers that are blocked at work, sorry if it's the latter)
i have 2 true percula clowns and a six line wrasse in my 20 long. My six line has tons of personality and I really like the coloration on them as well
i like the rock work.
seems awefully quick to add fish though and hardly time for the tank to cycle.
That skimmer might be fine for now but I had an Aqua C Remora on a 29 gallon tank for awhile and it was absolute crap, it hardly pulled anything out of the water. I would look into a better skimmer if you can