Nice tank. Nano's are fun. I've had a couple on my desk at work.
I'm not a fan of fish outside their normal temps nor of those gobies. But that is just "my" opinion and nothing needed here. They are cool looking though.
One mans opinion - nano's are cheaper if you can steal from your main display tank or sump. Or maybe from a friends. Tank and lights would be the biggest cost. Tanks shouldn't be too much. Can find a 1 to 6 gallon for under 40 bucks, cheaper if you scroung around.
No need for a skimmer on such a small display.
Live rock, sand, and rubble - from display or sump (yours or friends)
Water movement cheap power head or small koralia works great.
Lights - I'd go buy a meanwell driver and maybe 2 white x 2 royal blue led's and you would be rock solid on keeping anything with no extra heat what so ever. Lights - like fish - are all personal preference and carry their own baggage I guess. Seems LED's are catching on and I'm a DIY type of guy - so its on my next nano project list
Lots of fun though - and nice tanks!