I just upgraded from a 56 gallon to a new 120 gallon after a year and a half. If I were you I would do this:
1. Buy a 20 or 29 gallon glass tank and then measure the width. Go to a local glass shop and have them cut glass rectangles, or baffles, for the sump. I had a local shop make mine and I paid $16.00 for 4 pieces, so it's cheap. I made a sump with a skimmer section, a return section, and a refugium section. Total cost is like 50 bucks. You just buy some aquarium safe silicon for the baffles and silicon the glass in place.
2. Buy something like the Carib-sea Dry sand. I got the Fiji pink, but it's a medium grain. For a 55 gallon tank I would get a 40 pound bag. Next, get a bag of the Carib-sea live sand. It already has some bacteria on it and will seed your other sand. Get a 20 pound bag, so now you have 60 pounds of sand and will make a decent deep sand bed for a 55. Also, if you can, get a cup full of sand from someone locally that has a disease free older saltwater tank to help populate your sand's bacteria population.
3. Use alot of dry base rock, like from marco rocks. It would be alot cheaper. Then, just get a couple of pieces of live rock from someone or a LFS and it will seed the base rock.
4. I would put the dry sand in the tank with the dry base rock and fresh RODI water (do not use tap water, it MUST be RODI water). Then, add your salt to make the salinity 1.025-1.026. I would already have a couple powerheads in the tank to help mix the salt. For a 55 gallon a couple Tunze 6045's or a couple Koralia 4's would be fine for LPS corals and some SPS corals. Your salt will mix very fast and it makes it easy. After about a week, add your live sand and live rock to really help the cycle. The sand will settle out in a couple days.
5. Do not skimp on lights if you want any corals. I would get a couple 250w MH lights if you want SPS, if you only want LPS and zoanthids, then a decent T5 light with a good reflector should be fine.
6. You need a skimmer. You don't have to buy a high dollar bubbleking type skimmer, but you need one to remove pollutants from the tank if you want corals. I bought a used MSX 200 skimmer on RC for cheap and it skims awesome. There are many decent skimmers for sale on RC and you will not be sorry if you get a decent one now. Good water quality= nice corals and healthy fish.
7. Add fish after your cycle. Wait until you have close to 0 Nitrates, Nitrites, and Ammonia. You can add a CUC (clean up crew- snails, hermits, etc..) just before then to assist with any algae. Don't overstock your tank. 1 inch of fish per 2 gallons is a recommended amount of bioload.
8. Go SLOWLY....nothing good happens fast in a reef aquarium

