Spending tons of money on "cured" live rock at the store is a big expense. Being that you are setting up a smaller tank you won't want to overfill the tank with rock. You can get some base rock or live rock from fellow reefers that already overbought some

Then if you want some good coraline covered stuff you can buy a couple nice pieces from the local fish store to seed the tank with. A good thing to do is to do what we call "cook" the rock. The goal here is eliminate pest anemones and remove algea, detritius and other built up nasties off the rock. All you need is a cheap plastic tub, heater and a powerhead. If you are getting rock from someone that already had it in saltwater these are few steps to take:
1. setup a tub with a heater and a power head to agitate the surface of the water.
2. Mix up some saltwater with RO or reverse osmosis filter water to 1.026 SG (you'll need a refractometer) The cheap plastic floation models are junk.
3. Heat the water up to around 75 degrees.
4. Put some mixed saltwater or RO reverse osmosis water in a 5 gallon bucket.
5. Take the new rock you bought and swish it around in the 5 gal bucket and scrub it down. Swish and scrub it some more.
6. Move the rock into your plastic tub and let it sit for a few days.
7. You'll need some test kits for Ammonia and Nitrates. Test the water to see where those levels are.
8. Every week change out 50% of the water with fresh saltwater. Scrub and Swish the rocks some more.
9. Change some more water
10. Once you are at 0 ammonia and no more nasties are washing off. You should be ready to put in your tank.
Get back to us in a month and we can go onto the next step.