I always recommend starting with at least $500. But obviously, the higher your testing budget, the better.
My strategy is centered on being as lean as possible on the testing phase, and then be aggressive in the scaling phase.
I teach how to test 1 product for as little as $5/day for 5 days. That way you keep as much of your money as possible for the scaling phase. I will go over exactly when to cut and when to scale a campaign or adset, and what to do when you scale.