Don't go purchase ammo or brass just to blast away with it to "fire form" the case.
If you are going to purchase brass either new or used, do a load work up with it. An accuracy load that has been worked up with virgin or once fired brass will still be an Accurate load when fire-formed and loaded again.
Fire-forming will not take a "Bad" load and make it an "Accurate" load, just as Fire-forming will not take an Accurate load and turn it into a "bad" load.
Use all your time and components wisely to find that magic bullet/powder combination.
If you feel you must use "fire-formed" brass then form it without a bullet saving barrel wear and components.