Originally Posted by Dmax
$300 is not a lot to work with. You probably have to go for something pre-owned or second tier manufacturers like Hipoint. You can also check out surplus. In pre-owned you may wish to check out Taurus (PT92, PT99) or Glocks. You probably looking for Double Action/Single Action instead of Single Action Only.
I wouldn't go for a pre owned automatic, myself.
9 mm ammo will be cheaper, and the cheaper it is, the more you should practice, being a better thing
why do you need a handgun for self defence? have you considered, rationally, what your self defense needs are?