So I am thinking about a shotgun but I know just about zip about them. I am told you can get Remington 870's on sale for a decent price at Bi Mart or Big 5 if I pay attention. Do I want your basic pump action? Pistol grip? 8 shot tube? 12 or 20 gauge? What kind of ammo do I want to practice with and what type do I want for defense? Thanks!