You'll want to get the salt mixed into the water before adding the sand. I work with live sand, the aragonite mixtures work well, but if the SPG isn't stable, you can easily kill any good bacteria culture the sand brings in. I would target a SPG of 1.023 for working with clownfish.
You'll also need a hydrometer or refractometer to measure SPG/Salinity. The first week will be spent with a bare tank of water getting salt levels to where they should be. If wanting to do "nemo" fish, I will suggest a reef tank? Starfish, anemone, clownfish, a few shrimp and a cleaning crew, and it could be beautiful... maybe another small fish or 2, depending on the species/sizes. Firefish (goby) are really sweet, as are some of the other small goby species. If working with anemone, watch the lighting you use. For a "nemo" aka ocellaris clownfish, you'll want a bubble anemone. Be forewarned, tank raised clowns don't always take to an anemone, many of them don't know what it's for. Wild clowns will understand it.
Anyways, water and salt, then sand and liverock. When I put my sand in, I try to do it right after the liverock is set, so to anchor the rock better with the sand. After this, another couple of weeks of watching and water testing as your tank cycles. Average amount of time from water to fish is about 4 - 6 weeks. Each tank is an individual, so some may take longer, some may take less.
Once you're cycled, go easy when adding animals, not everything at once. 1 - 2 animals every 2 wks is a good pace, giving the system a chance to stabalize after each addition without any severe spikes to harm anything. Or, in the case of snails or blue leg hermits, a dozen at a time for small stuff, turbo and other large snails, up to 3 at a time in a tank of that size.
Suggestions for starfish: brittle and serpent stars, linkia stars.
These tend to be good for beginners. Linkia stars eat algae, so you'll want to make sure there is a food supply for it before introducing in to a newer tank. Brittle and serpent stars will scour the sandbed for food, and will eat frozen formula food, once thawed and warmed to take temp.
Be careful which starfish you select, as some, such as chocolate chips, cushions, and a handful of others, are predators, and will eat fish if they get the chance. Cushion stars grow huge, so you'll want to shy away from those, that's another species shouldn't be sold on the open market.
Then, if lighting is proper, you could add corals...
If you're planning to use the hang on filters, the skimmer is a must, and you might want to consider protecting your wall behind the tank and filter so it isn't damaged by salt creep.
Salt creep is one topic I haven't seen mentioned, but it's something everyone will experience to some degree with a salt water tank. Because of the way hang on filters have a tendency to "splash" a fine mist of water, the water evaporates and leaves the salt behind. I have seen people's walls totally destroyed by neglected salt creep, to the point of having to replace the drywall. The 92 corner bow I just set up in a Dr's office has a sheet of plexi glass on each wall in the corner, and sealed with silicone where the pieces meet. This works well and is easy to clean, without blocking out the wallpaper behind it.
You'll also need a heater and thermometer. I suggest a good submersible heater, able to handle the salt content. EboJaeger makes a good one, but they're expensive. AquaEl makes a good one, but a portion of the price if you can find them.
When setting up your filter, remove your carbon. Carbon in a saltwater tank is used only to pull out meds if needed. Carbon left in the filter will deplete the tank of mineral content the animals need to survive. If you run carbon, be sure to dose regularly with trace elements, and to test for them frequently.
And, last but not least, a good set of liquid test kits for ammonia, nitrite, nitrate, pH, calcium, and KH. These will be most important, though you may find at some point there is a need for another here and there. These are the kits you'll want to have on hand for regular use.
Good Luck with it and keep us posted!
Let us know if you need more help.