This question comes up and causes debate every few months. Do your due diligence and research, particularly on the CMP forums. I did nearly 50+ hours of research when building my Garand and then modifying it to match standards. The general consensus is any commercial loading between 110 grain and 180 grain projectiles is fine for the Garand as long as it isn't some ridiculous hot load. They were designed for 173 grain bullets on a healthy charge of powder (M1 Ball). Once you start going into the 200+ grain category, an adjustable gas plug would be an OK idea. I run a Schuster adjustable plug in mine because I have some hot 190 grain long-range loads I wanted to try a while back. Realistically, the heaviest useful projectile in a Garand is something in the 175 grain range for match loads.
If I were you, I would buy the cheapest 30-06 commercial stuff I could find and just run it through if you don't reload.
If you want some modern stuff super-tailored to the Garand, Hornady Garand Ammo is the Holy Grail. A 168 Grain A-Max over 46.5 grains of Varget. They have tailored this load with their CMP, NM, and Garand Match shooting teams and is the best factory Match ammo for a Garand.