Step 1, move out of the ghetto.
Step 2, go with a short barrel 12 guage shotgun. Some guys favor slugs, but honestlt, some size 7 1/2 target loads are gonna vaporize anything they touch. Pattern size is huge, you don't have to be as precise as with a handgun, which require a fair amount of skill and experience for a rookie to accurately place a few shots during the scramble and heat of the moment. Much more room for error with a shotgun. The control and accuracy with a shotgun can't be beat.
Also you don't have to worry about sending your .45 round through your neighbors wall and hitting one of his kids.
Step 3, buy a handgun as well, before they outlaw them. .40 glock or similar model is a great starter gun.