1.(Equipment) Most nano cubes already bring most of the equipment that you'll need except a heater. If you live in a place that drops below 30F or doesn't have central A/C then it would be a good idea to have it. A thermometer. Tropical ocean temperature is between 70F-80F. You're going to need a hydrometer to test salinity & test kits to test water quality. For a fish only tank you need to check ph, ammonia, nitrite, & nitrate. every month or two weeks. For corals you'll need to check ph, kh, ammonia, nitrite, nitrate, phosphate, calcium, & magnesium every week to three weeks. API has really good test kits. You'll also need the individual bottles of those different elements (calcium, KH, & magnesium) again, if you want corals. A fish net. Their is also a product called "phosban" that will absorb phosphates if you're going to use corals. It comes in a little bag & you can place it were the filter floss is. Not required but good for a small tank.
2. (Setting it up) You mentioned you wanted to use live rock & sand. Just wanted to let you know that you can use what ever decoration & substrate you want. It really doesn't matter. You could have pink gravel if you wanted. Just along as you rinse it as always of course. It's a common misconception of saltwater fish keeping that you can't. Don't let anyone tell you otherwise. Believe me you'll be fine. If you're going to use live rock I would personally recommend fully cured purple Coraline live rock or just dry rock. It's just that live rock that isn't cured comes with a lot of different organisms in it like many different worms that at least for me are pretty ugly. The water can be purchased at the fish store or you can make it you self with salt mix like instant ocean for instance. If you're going to make it yourself you're going to need purified water from an R/O (reverse osmosis) water filter unit. The problem with using neutralized tap water is that it has a lot of minerals & devolved organics that can cause a lot of ugly green algae growth & in some case cloudy water from chemical imbalances (calcium precipitation). First put in gravel, pebbles, or sand & even it out. Then set up your decor or rock. Make sure the rock is well set into the sand & make sure any rock on top of each other can't tumble over. Then add your water. Do it slowly if you're using sand that way you wan't have to wait a day for the sand to settle. You can use a siphon to get the water from the bucket to the tank without having to dump the water in.
3. (Adding livestock) If you're using live sand like nature's ocean we can add a fish immediately after the sand completely settles. Then introduce the rest the next month. If you're not going to use live sand then you'll have to wait for bacteria to develop in the water so that when your fish produce ammonia the bacteria can convert it to nitrite & then nitrate. you'll have to wait at least two weeks. If you use a bacterial product like viraspira or cycle you have to wait one week. When you add the fish you have to acclimate them. You have put the bag in the water for 10 minutes to match temperature. Then over a period of 30-120 minutes (depending on species) you're going to slowly replace the water of the bag with your water. You can use a cup & kind of eyeball how much you have to take out evenly spread over time. Then you dump the remaining water into the sink & bring your fish onto your aquarium using a net. If you don't acclimate saltwater fish they'll die within hours. Most people choose to keep 3 or 4 fish that are no bigger than 3-3 ½ in. in those tanks. Most people feel very strongly about this. I just think it's more a question of morality than anything lol. Here's the controversial part… It's fish not a? dog. Fish tend to grow to the size of their environment. While yeah putting a large fish in small space will eventually? stress it to death, putting a juvenile in a reasonable amount of water closest or as near as possible to the fish's max size wont really result in any major long term stress except stunt growth & perhaps life to trivial amounts. In any case though putting any animal in an inclosed space will add some stress no matter what. Not all fish are compatible. Aggressive fish can't be kept with peaceful fish. Some fish aren't compatible with corals or invertebrates. Carnivores can eat other fish smaller then them. Some fish can't be kept with their own kind all though these guidelines can be bent depending on how big the tank is.
4.(maintenance) You have to do water changes. You can do either 5% every week or 10-15% every two weeks. If you want to refill do to evaporation you have to use R/O filtered fresh water so that way you salinity doesn't go up since when water evaporates the salt doesn't. Try not to wait to long before there's a lot of evaporation because remember the ph of freshwater is 7 & for saltwater it's at least 8.
Well that's pretty much all I can think of lol. It's a lot to read but hey it's ALL THIER. Enjoy your tank & good luck!