First and foremost - DO NOT select a gun just because your friend says it is the best! Do your research. Go to a gun shop and hold the handgun. When you are considering the purchase of a firearm, whether it will be your first gun, a backup piece, or just another addition to your collection, there are several things you need to keep in mind.
Find something that fits your hand.
Find something you will be comfortable with carrying every day.
Choose a caliber you can handle, but with sufficient stopping power.
Seek advise from a professional such as at the gun shop.
If at all possible, try and shoot the gun before purchasing. Maybe a friend has one you can try at the range.
One of my personal choices (key phase: personal choice) is the Stoeger STR-9 in 9mm. It is extremely affordable (typically under $300) and very reliable. I have both the full size and sub compact size. To date, I have fired upwards of 10,000 rounds in the full size and about 3,000 in the sub compact without a single malfunction in either! Yes - that is amazing. Here is a video comparing the Full size and Sub Compact size STR-9's.
Remember!!!! No matter what gun you eventually select, it is only as effective as how much you train. The gun does not do the work - you do. So train often, be responsible and stay safe!