While I still believe that a good old 12 gauge with double ought buck is the best self defense weapon around anywhere, if you must carry a pistol get one that is easy to handle and get some training and lots of time at the range.

Understanding that bullet mass is important, it is more important to be accurate and the bigger the projectile the less accurate you will be, especially as a novice. The 22 target pistol will do the job, especially if you really know how to use it. Personally I have a S&W 9mm M and P that is fairly easy to learn and shoot with accuracy and a Sig Sauer P220/45 which is a handful and a bit more challenging to shoot accurately. Big caliber short barrelled weapons are the worst for comfort and accuracy, try a Glock 45 should you want a graphic demonstration.

Should you choose to upgrade, I would recommend a name brand (Smith/Wesson, Colt, etc.) and a weapon that is still in production. These guns all need some maintenance and all need routine cleaning, if you lose a spring or screw out of an out of production weapon you may play hell trying to find another.

While the Gun Broker is a very good resource, I would advise against buying anything from that source unless you are very familiar with the weapon offered. Go to your local gun dealer and find something that you like and is comfortable to handle, to disassemble, and to shoot....then and only then it is safe to go to the Gun Broker.