Clean tank a place it. Don't not set it up right against the wall. Leave room to comfortably accesses the tank from behind or possibly add a sump behind the tank at a later date.
Go to LFS and purchase;
1 bag of quality salt mix. Enough to make up 50 gallons. About 20 bucks
1 Maxi jet 900 power head. About 30 bucks but much cheaper over the net.
1 hydor flow deflector to attach to the power head. About 20 bucks
1 Hydrometer. About 15 bucks
Stop at Walmart on way home and purchase;
3, 7 gallon water jugs in the camping/sporting goods department. About 21 bucks.
Walk outside or next store to the grocery and find the RO water machine and fill the jugs. 30 cents a gallon.
Go home pour water in tank. I know, its not full don't worry. Mix in your salt mix and shoot for an SG of 1.025. Dos not have to be exact for now. Place your power head below waters surface and plug it in. Day one complete.
Day two start shopping around for some live rock. Get as much as you can afford up to 40 pounds. I know this is expensive. You can also use some suitable base rock but no more than 10 pounds or so for your system. Cured LR can also be added at a later date as you can afford it. Go home and place the rock on bottom of tank. Take a break.
Day three sand. If you can afford LFS argonite fine if not go to Home depot and get play sand. Use a piece of 1 inch PVC and slide the sand down through it to the bottom of your tank around your rock. Shoot for about and inch and a half. Ya I know tanks cloudy, don't worry. Now top off the tank with pre mixed water at 1.025 SG and make sure the power head is circulating the water nicely. You can also put a hang on back filter on the tank at this point but its not mandatory. Now ghost feed the tank every other day for a week with a pinch of flake food.
Your done, check back next month. Do not add any fish. Top off any evaporation loss with fresh RO water. Keep tank water around 79 degrees. May need a heater for this.