I prefer to start with new brass. Buy 200 or so and you can zero and load an easy ladder test at a few hundred yards with under 50 rounds. Load the other 150 based on the ladder results and you have enough to shoot a club match or two.
At the end of that you will have nice brass that’s fire formed to your chamber. Begin your load testing in earnest. It shouldn’t be that different than before but it won’t be the exact same.