Cheap ammo, low cost and reliable firearm, and not caring about size? Get a Smith and Wesson Sigma 9VE (yes, they are VERY reliable since the E version, about 10 years ago), and 9mm is cheap and plentiful. Figure $250 for the firearm (typically $299 with a $50 rebate right now), and $25/100 rounds for factory new ammo, $17/100 rounds of reloads.