For what it's worth, I get 5-7 mags per pistol. I pre- load them before I go to the range, 2 with my carry, self-defense load (until I've had 100 flawless rounds with that ammo), and the others with FMJ target ammo. If you get rid of a pistol, mags are easy to sell.

Practice (with good habits, by training by an experienced instructor if necessary) is the best accessory.