You can buy cheep, dry, base rock to cycle the tank with. You don't need to buy any LR. After the tank has cycled, you can cherry pick LR one at a time. Like wolfe4372 suggested. It's much cheaper that way.
Here's a link to some cheap base rock. I've never purchased from them but I've heard good things from those that have. http://www.marcorocks.com/index.asp?PageAction=VIEWPROD&ProdID=59
If you want to mainly use uncured LR airate the h*** out of it in your tank for a couple of weeks. Then once your levels even out do as EC says and cherry pick a few nice pieces, leave them in there another couple of weeks then you should be fine.
Get some cheep 50G garbage cans fill them 2/3 full of UCLR top off with SW then put a air pump with air stone in each can cover them in the garage or outdoors, do a 50% WC a week until the rock is ready about 2 to 6 weeks.