Equipment and ammo will start matter when you achieve the expert level in your shooting career. By that time you will know what you want from it and adjust it. For starting, any reasonable accurate stock gun and low grade standard velocity ammo do just fine. Don't overthink it, but concentrate on your own skills and shot execution. You will know when gun or ammo start limiting your progress.
I have boosted confidence in equipment of many shooters by picking up their guns and ammo and shooting very tight groups. They see right away that gun is capable of and don't question it for a long time. They call it showing off, i call it demonstration.