Do not use fish to cycle the tank. Buy some live rock, and that will cycle the tank for you. Or you can add some fish food or a piece of frozen shrimp (that people eat) to the tank, and when it starts to rot the cycle will kick off.
You won't want a deep sand bed in a 29 gallon tank because the sand will take up too much space. You should probably get sand that's 1 to 2 inches deep. This will be enough to keep your tank clean, but probably not enough to keep a sand sifting goby if you were planning on that type of fish.
1 to 2 lbs of rock will be perfect. So 30 to 60 lbs of rock total. To save money, you can buy some live rock and some dry base rock. The live rock will quickly seed the cheaper dry rock, turning it live in no time.