In a 55gallon i would only go with one beardie, if you want to add a mate i would upgrade to at least a 75, but a 125 would be better.
Feed your baby as much as he will eat at a time, and trust me, this will be a lot. My babies used to polish of dozens and dozens of crix a day! Not to mention veggies and the occasional worm.
I agree with Sean, sand is never a good idea for baby beardies, and many people dont even keep their adults on it. It can cause impaction and is tough to clean. It also makes the tanks REALLY heavy. As babies, i would use paper towels or newspaper, not very attractive, but it may save ur babies life, and its MUCH easier to clean.
Once your baby is over 6 months, usually, you can put them on sand if you want to. the best sand to use is very fine grain, washed playsand, its cheap and available at any "home depot" type store.
Never never never use calci-sand, vita-sand, or any other sand claiming to be digestable 
For decorations, you want a couple of good sturdy basking spots. I use driftwood in my tanks but you can use large rocks if you want to. Aquarium decoration rocks work well, but they are pretty expensive. If you bring something inside that you found on your own, make sure to sterilize it througholy.
good luck 
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1.0 green iguana-Deitrich
1.1 Common Boa-Un-Named, Ursula
1.0 Ball Python-Anabell (go figure!)
1.0 Red Tegu-Uteg
1.0 Albino Cal King-Pig
0.1 Mexican Black King-Morticia
1.1 Bearded Dragons-Unnamed, Hanabil
1.0 Albino San Diego Gopher-Unnamed
0.1 Hermans tort-Esio
1.1 JCP-Milton, Medusa
1.1 Reverse Okeetee Corn-Unnamed
0.1 Snow Corn-Unnamed
1.0 Hypo Okeetee Corn-Unnamed
0.1 Motley Okeetee-Unnamed
1.0 Western Hoggie-Wyrm
0.0.1 Rose Hair Taruntla-Unnamed
2.0 Leopard Geckos-Reptar, Pogo
4.1 cats-Tucker,Poe,Abhib,Emerald, Felicity
0.1 Bullmastiff-Asha