I don't know what kind of muzzle loader you have but my young son at the timestarted out shooting 30 grains at 25 yards and 40 grains at 40 yardswith a .50 caliberpatched round ball. This was just for punching paper and becoming accustomed to learning how to shoot a muzzle loading rifle.
A friend's wife tried one of my .50 calibersidelocks for her first time and sheenjoyed shootingpatched round balls with 50 grains at 50 yards.
From there the load can be increased in 5-10 grain increments to suit her recoil sensitivity, and depending on the distance to the target, the weight of the projectile firedand accuracy results.
Remember, more powder means more fouling residue.