If you have made the decision to buy a gun, it probably means you are coming to grips with the sad state of the world, the nation, and where you live. It's a decision millions of people have made in the last several years alone. It is one that reflects a change in your outlook and possibly your lifestyle, since many people who buy a gun for home defense go on to concealed carry for personal defense. What you do next is pretty important.
There is an old saying that goes something like "buy quality and only cry once", or something like that. I once bought one of the low price guns mentioned here. It went back to the factory twice, and the third time the dealer sent it back for good. I replaced it with a quality gun for twice the money. Why do law enforcement and military use Glock, Beretta, Smith & Wesson and some other well known big name guns? Reliability and durability, and the ability to hold up under hard use and abuse. A handgun, especially a semi-auto, is a complex mechanical device. Do you really believe a $300 gun can be as good as a $600 one?
Second point. A gun is going to be the second most dangerous thing you own, next to your car. You learned to drive before you bought a car. Do the same thing here, and you'll be glad you did. Yes, shooting lessons will use up some of the money you were going to use to buy a gun. Save up, change your spending habits. Don't buy that new iPad or 3D television or fancy camera. Don't just join some Internet forum and ask, "What gun should I buy?" OK, you started out with the worst possible approach to the problem. Now do it right.