Okay so the 55 gallon tank isn't really appropriate for an adult dragon as it is too narrow. The baby could be in there for a while, but as it is only 12 inches wide, it will be a problem in a matter of months. The minimum floor dimensions for an adult should be 36" long by 18 " wide. However, here is the complete list of stuff you will need. You will need a LOT of crickets. Max was going through about 150 crickets every 4 days before he decided he didn't like them anymore (my fault, I introduced roaches and superworms). I personally hate them, and use dubia roaches instead. If I were you, I would research the roaches, and start a colony 4-6 months before you get the dragon. Then you don't have to worry about buying feeders (except as treats). Crickets are smelly, can bite your dragon, stink, escape, and die off in droves. Dubia roaches are quiet, don't smell much, can't really climb, can't jump or fly, and live for a long time. I would also suggest trying Phoenix worms - I was going through 1,000 of them every 10 days or so when Max was little.
Ok - everything you need:
a) tank - as explained above.
b) substrate of your choice (but nothing loose) - I would highly suggest slate tile. It is very similar to their natural habitat, is cheap, easy to clean, keeps muscles toned and nails trim. Other options are reptile carpet, non-adhesive shelf liner, and paper towel/newspaper. Your call really.
c) basking spot (rock or log, either from outside and sanitized, or bought)
d) hide (don't use this for the first couple weeks so your baby doesn't hide instead of bask and acclimate)
e) other tank furniture (a log, a fake tree, vines, fake plant... whatever you want. Just browse the pet store)
f) basking light (whatever wattage gets you to the right temps (105-115F basking spot)
g) basking light clamp lamp fixture
h) 3M command hooks
i) under cabinet fluorescent fixture (I got mine at Walmart - I had a heavier one from Lowes, but it kept falling)
j) ReptiSun 10.0 tube
k) Digital thermometer with probe (at least 1, and they should have a hygrometer built in to measure humidity) and/or temp gun
l) a food bowl for salad, and another for worms/roaches (no water bowl - they don't need a water bowl, and it will just raise the humidity. Just be sure to give baths. Do not feed mealworms a bearded dragon, but you can put phoenix worms, silkworms, dubia roaches, waxworms [treat], butterworms [treat], or hornworms [treat] in a bowl)
m) If the tank gets below 65F, another dome fixture and a ceramic heat emitter (do not use a red light)
n) (Optional, but really really useful) a power strip with built in timers for lights.
Make sure that you are offering baths. For a baby, that should be every other day for 15-20 minutes in shoulder high luke warm water. The baby needs to be monitored closely in the tub so he doesn't aspirate water.