Most of us probable got into the shooting world via a shotgun or 22lr rifle.    Those seem to be some of the best instroductory firearms.    You can learn the basics about shooting from a 22lr bolt action rifle and the shotgun is the most versatile firearm out there.    Something like a Remingto 870 shotgun is normally available with an 18-28 barrel on it and can be found in 12 or 20 gauge.   The shotgun can be used for pheasant hunting all the way up to deer just by altering the type of shot or using a slug.  Depending on the sights you have on the gun, you may want to consider rifle sights if you plan on using slugs very often.
The shotgun is handsdown the most effective close range weapon.   I’ve demonstrated the use of Ar15s and handguns against targets under 50yds and then shown students a Remington 870 using buckshot and there is always a clear winner when it comes to hit ration and damage done.   A shotgun may be a powerful tool and possible too much for some users, but you can easily modify an inexpesive gun show find that costs less than $200 to a practical defensive shotgun.  Advanced Technology Stocks have a few updgrades and add ons that will give you comfort when it comes to choosing a home defense weapon.