Population increases will come by themselves, there realy isn't anything we can do to assist that (except increasing the percentage of children that survive to adult-hood through nutrition, and other such things, which we can increase through higher living standards).
Metal working was invented almost right after agriculture historically, as the knowledge of metallurgy opens up a much wider variety of tools than stone tools do.
We need agricultural tools to achieve the levels of productivity necessary to maintain and increase our agricultural surplus. Plows (ploughs), hoes, shovels, all simply can't be made out of stone. (possibly bone, with the aid of precise tools to shape them)
By refinement, I assume you mean some sort of class structure were there is a defined warrior class, maybe some sort of priest hood, a ruling class certiantly, a scholarly class, merchent class, and the supporting state bureaucracies?
For all those we need to pull as large a percentage of our population out of farming as possible, and the largest in raw numbers. That all will require advancemnets in agricultural productivity, which we can only achieve through increased tool usage.