Get an adjustable gas cylinder lock screw (aka gas nut or gas plug), so that you can shoot commercial ammo. (Except for Light Magnums...)
I know of two varieties, the Schuster and the McCann. Each accomplishes venting in a slightly different way, and either works.
For reloading, I'm getting pretty good results with Hornady 150 gr FMJBT, Varget and Winchester brass.
The latest Hornady manual has a section on loads for the Garand.
.30-06 Springfield: 100 yrs + and still going strong