I'd shoot for more like 30 lbs. I have Lalo rock in one of my tanks and Fiji in the other...been happy with both. The main thing is to be sure that you are getting more porus rock in order to get the full filtration benefit. Anything sold as base rock is likely to be denser, less porus, and therefore less beneficial for bio-filtration.
fiji i believe is the least expensive live rock you can get AND its generally good quality as long as you choose good pieces. The general rule is 2 lbs. per gallon BUT i dont think you normaly put that all in if you want any space! I havea 40 gallon with about 60 lbs. in it. So a basically 30 gallon i would think you start off with about 30 lbs. and if you plan on adding coral that will add some pounds or if you happen to find any good pieces when just browsing you could buy them. I would try to make sure theyre cured otherwise thats a whole other process.