I buy 100 pieces initially, do seating depth testing to gain once fired brass, then do powder testing, then primer testing in that order.
Full testing is then done with the best powder and primer.
I only minimal size the body if necessary, and the second firing is only done with neck sizing and a mandrel.
After the first 100 are fire formed 3 times, measured and sorted, I will often buy another 100 cases and fire form those and sort.
My 6.5x47 has 800 cases, did have a bulk lot of 1000, but a buddy needed 200, so I sold them to him.
Initially, on a new gun, if available, I will buy 200 pieces straight up, but sometimes, like my 300RUM, there was no brass available, so I bought 100 factory loaded cases and ran the barrel in with those.
Cheers.