Depends on how much sand you want. I've got about a 80-90 lbs or so of live sand in my tank.
As far as LR
goes are you wanting to use it to cycle your tank? Again, just what I did - but I have about 90-100 lbs of rock in my tank. About half of it was purchased as cured LR
and the rest was base rock. Base rock is about half the price at worst, sometimes it's cheaper than that even. But the general rule of thumb for a reef tank is 1.5-2 lbs per gallon of rock.