You can definately use base rock for a majority of your need. The filtration benefits of the rock are not determined by the life it comes with. If you only use 15-20% LR
for the remainder, the fauna and coralline (light depending) will multiply in time.
With just a HOB
filter I would suggest close to 75 lbs total for the tank. 50ish lbs would be the minimum. I would also suggest at least one more PH
to help with the water flow. A maxi jet 1200 placed at the other end of the tank from the HOB
will improve things a great deal. If you are intending a reef tank, I would actually suggest two.