There are many components to an effective Home Defense plan.The first thing most people consider is a firearm and I agree that is probably a good place to start for most people.First choice is a handgun as they are relatively affordable,portable and can be carried around easily in confined spaces.There simply isn't much operating room in most homes for a long gun and many times a burglar or home invader will be in very close proximity to you during a confrontation & a long-gun such as a rifle or shotgun would easier for him to disarm you.
With a handgun you have one hand free to open doors,dial phone,lead a loved one to safety or whatever you may need to do in a crisis situation. Concealment can even be an issue at home when you answer the door to a stranger and to do so armed with a rifle is inappropriate and would alarm neighbors.Or what about stepping outside to investigate a noise you heard in the garage or in your backyard. A small handgun concealed on your person or held behind your back doesn't alarm others that you have a gun.Effective Non-Firearm weapon options include Pepper Spray,Impact Weapons,Knives,& Taser's.
Barrier's(Locks/Sturdy Doors & Windows)should be a priority as well & often overlooked.Alarm systems,security camera's etc. are possibilities for those who can afford them.A baby monitor in another room(especially Child's irregarless of age)is a cheap alert system for you to hear a possible breaking & entering.There's also remote light switches(allow you to turn on light from behind door)as well as various locks/blocks/braces can com in handy.Surveillance and the like is a good addition,but a weapon is still a mandate because not every assailant will be deterred from harming you & your family by an alarming going off and may break though your "barriers",so a means to directly protect you & yours is always needed.
Some Specific Weapon Recommendations:
Handguns-Glock 17,19,26(NY trigger good option esp. for beginner)
Smith & Wesson 640
Ruger SP101 Hammerless
Pepper Spray-Sabre Red(large models available for Home Defense)
Knives-Small/Carry outside.... Spyderco Clip it's(Endura & Delica)
Large Cold Steel 6-8 inch Blade
Ka-Bar 7-8 inch Blade
Kitchen knife in a pinch
Impact Weapons ASP Baton
Any durable wood,metal pole or even baseball bat(cold steel even makes a polymer one)
MACE makes affordable individual door/window alarms
Surveillance-MACE has a whole line of affordable products
Strict budget- Baby Monitor,remote switches etc.