Are you looking for effects to be done in production (SFX) or in post-production? (VFX) or both?
A few things
1) A gun would have kickback, so the actor needs to simulate that. To get them the proper feeling for it, have them hold the gun, then (lightly-ish) punch the front of the gun with your fist/palm. That's the motion they need to emulate when firing. Nobody could possibly fire a real gun as quickly as he was pulling the trigger. Have him feel the shots.
2) Don't worry about the smoke as much as the muzzle flash - the bright flare that comes out the barrel of the gun when the bullet's fired. Google will give you 10,000 muzzle flashes to get started.
3) Environment effects - it's possible that, being in a fairly dark room, the light from the gun would light up things around it. Try setting up another light on a switch you're able to flip on and off quickly, and practice synchronizing it with the actor's gunshots (since you're going to be adding gunshot sound fx in later, feel free to just say "FIRE, FIRE, FIRE, FIRE" when you want the actor to fire each time).
4) Sound is incredibly important.
