Just one...start with a .22, or better yet a CO2 powered Airsoft pistol it's a LOT cheaper than a 9mm or above. If you're in an area where you can shoot after dark, that's great.....easier to not
cheat using a pistol w/o night sights.
There was a recent report put out I saw on PoliceOne.com or Officer.com (can't remember which) researchers found that most LEOs involved in shootings didn't use their sights at distances closer than 15 yards, regardless of lighting. From 15 yards and further all of them used their sights.