Yes it is a start. You can add more as you go. Just be careful about adding live rock after you have cycled and added livestock. New additions could start a new cycle if the rock is not completely cured causing toxic conditions for your livestock.
Oh ok that's good then .. The fish store has base rock and I'm just going to stack them. I don't want any plate rocks anyway. So how many pounds of base rock will be good. It's 5$ a pound ?
Base rock is not as efficient since it is not as porous as other live rocks meaning you need more than you would per gallon than the better rock which is why it is so cheap.