What I recommend to save cost is to get 2-3 pieces of the best rock you can. The good stuff that's covered with coraline, sponges, little duster worms, algae, etc. and make up the rest with dry base rock. Base rock is usually less than half the price, and all the life from the other rocks will seed it pretty quickly if there is food available.
Someone stop me! Please! But... not just yet...
55 Gal Tropical FW
55 Gal Mixed Reef