1) Get a gun.
Duh. You need a gun to adequately protect your home. Your dog will bark. ADT will call the cops, and they will show up in 7-15 minutes. Meanwhile, there's an intruder in your home.
So what do you get? For the homeowner on a budget, you have two options. Cheap handgun, or pump shotgun. I personally think every man of "fighting age" (18-38 years old) should have a shotgun, handgun, and field rifle...and they should be purchased in that order.
A lot of people look at the 12ga and think it's unusable for home defense, especially when it may be used by a woman. Nonsense! The 12ga is actually the best home defense weapon available. It projects a lot of metal downrange, with almost zero over-penetration danger. Standard birdshot will remove a person's leg at close range, and the recoil from such a load is next to nothing.
A shotgun is also very suitable for use in homes where small children are present. While all firearms should be stored where not accessible by children, a pump shotgun is perhaps the most difficult for a child to fire. On top of having the heft not typically handleable by a 40lb kid you also have the mechanics of racking the slide and kicking off the safety.
While "tactical" models are available, people on a budget should get a standard "duck hunter" model and take a hacksaw to the barrel...for no other reason than the fact that they're generally cheaper. It is completely legal to saw off the barrel of a shotgun, provided it is at least 18" long from breech face to end of the muzzle. If you go from the part where it mates with the receiver and measure those 18", you're more than good in the eyes of the law. You should be able to purchase a name-brand shotgun for under $300, including the Remington 870 and Mossberg 500. I recommend the Mossberg, because it has a tang safety instead of the cross-bolt of the Remington, but that's a personal preference.
If you must get a pistol, DO NOT get a revolver unless you are an experienced shooter. No, they do not "jam" like an auto pistol has been known to do. You are, however, limited to six rounds. A 9mm of equivalent weight of a standard-size .38 will give you 15 rounds...and the ability to reload quickly. The importance of this will be discussed in detail later.
When buying a pistol, buy SIMPLE. I have owned pistols ranging from .22LR target models to a .45 M1911. I recommend a Smith & Wesson Sigma 9mm, because it works. There are more than $10k worth of firearms in my safe. The Sigma is between my mattress and box springs.
2) Shoot to kill.
If you shoot and kill an intruder in the state of Texas, it's generally understood that it's going to be chalked up to "armed homeowner protects his family and property, shoots and kills criminal"...and that's going to be the end of it in the newspapers.
More than likely, unless it's a prior felon with a history of raping kids and setting live squirrels on fire for sexual gratification, you're going to be heavily questioned by the police.
The law in Texas states that you can cap an intruder who has aggressed upon the home. However, if the intruder lives, he can make claims that he knew you, he was invited in, etc. There is also the probability that he may sue you in civil court, turning things into a costly legal battle.
A dead man, on the other hand, can make no such claims.
In addition to the legal aspects of the situation, there is also the self-preservation angle. It is considered a fundamental law of gun safety, that you do not point a firearm at anything you do not wish to see utterly destroyed. This is why you never, even jokingly, point a firearm at anyone. PERIOD. You just don't do it.
Do not (I can't repeat this enough...DO NOT) pull a piece on anyone, in any circumstance, without the very specific intention of putting this person in a very non-alive state. If someone breaks into your home, and you choose to protect your home with a gun, you start pulling the trigger. You should not be stopping until your firearm is empty.
It's long-since been a joke amongst gun owners, regarding the old anti-gun adage that people are more likely to die by their own gun than shoot a bad guy with it. If this is going to be the case with you, let it be because you ran out of ammo and you were beaten to death with your pistol. In other words, do not stop shooting at your assailant. If he's twitching, he's moving...and if he's moving, he's a threat to you.
Repeat after me, kids. "I was in fear for my life. He kept moving, so I kept shooting." Stay at least three feet away from your assailant, for two reasons. First, there is absolutely no way a wounded assailant can harm you, when he is out of harm's reach. Second, there is no danger of anyone spotting "powder burns" on the clothing or flesh of your home invader, and claiming that you have "executed" him.
Keep shooting until you're empty. Then call 911. If he's still moving after you've called 911, reload and keep shooting. This is why you don't buy a revolver for your first pistol.
3) Practice with your weapon.
More importantly, don't be a dumbass when you practice. You're not hunting ducks, nor are you getting ready to audition for Annie Oakley's Traveling Road Show. You play how you practice, so practice accordingly.
First order of business is spending $50 on shells for your weapon and getting acquainted with how to use it, how it's going to act when it goes "bang", how you're going to react to it, etc.
When you get home from that first day at the range, you need to sketch out the floor plan of your home. It doesn't need to be a professional-grade blueprint, just a sketch showing walls and doorways. Take a good look at that sketch, and find out where the longest clear line of sight in your home happens to be. That "line of sight" is the distance where you can stand in one place, and get a clear view to another place.
On a 2500sqft home, you're looking at a structure that's 50 foot by 50 foot. Even if this structure were a perfect square, and you were able to get a clear line of sight to the opposite corner, you're still looking at 70ft. In all likelihood, your maximum line of sight is going to be closer to 40ft.
If possible, don't waste your time on a gun range that offers pistol shooting at 25 yards. That's 75 feet. Find someone who has some land in a non-incorporated (read: RURAL) area. Set up five targets each, at ranges of 5, 10, and 15 yards. That's 15 targets. Have a friend call out specific targets, and practice emptying a magazine into each one.
And yes, this works with a shotgun or pistol. Most importantly, practice. And then, practice some more...