[dhoward]

You don't buy powders based on price. The caliber, desired muzzle velocity, bullet type and weight all factor into what powder gets used.
Get a reloading manual from one of the major manufacturers, i.e. Hornady, Speer, etc. and pick a recipe from there.
When starting to reload, the last thing you want to do is go off half-cocked (heh, heh...)