I'm generally in favor of gun ownership, and in favor of mandatory training. I wish the government would provide/pay for training, but I wish a lot of things.
Before buying a gun, please consider:
How will you safely store it? Are children Ever over at your house? Can you access it from storage in an emergency?
Where, and when can you practice using your gun in a safe location? Typically, this means going to a range. It's best if you know an existing gun owner/range member to help you the first time. If you buy a gun, you should safely operate it on at least two days, to build familiarity.
What kind of gun suits your needs? Rifles are better for hunting, and other situations where time is readily available. Handguns are easier to conceal, store, and use. Shotguns are better at hitting things with poor aim, but they hit a lot of other things, too. Most guns are designed to fire one shape of cartridge (generally specified as a diameter and a length), but can support multiple types of bullet (full metal jacket, hollow point, and green tip are fairly common for rifles and pistols. Bird shot, buck shot, and slugs are common for shotguns).
Not all cheap guns are bad, and not all expensive guns are good. Generally, more popular cartridges and guns are preferable, because it makes obtaining ammunition, maintaining the weapon, and knowing of any design issues easier.
Accessories (especially a flashlight, or sights suited to the expected use) can improve the usefulness of a gun significantly. You will also generally want eye and ear protections for range use, and at least cotton swabs, a lubricant, and a bore rope to clean and maintain your gun.
Do you know your rights? Do you know the laws applicable in your area? In some states, there are laws about which guns you can buy, how you can transport them, how you can carry them, how you can store them, and how you can use them. You should know the requirements for lawful self defense (Andrew Branca's five elements is my favorite explanation). In all 50 states, there are laws about who can buy guns, and some restrictions about where you can buy guns. There are restrictions on how you can modify guns that apply in all 50 states.
If you can afford training, look up the instructor you will have. The individual instructor makes a lot more difference than the facility or institution, IMO.
If you, or a loved one that will have access to your firearm are, or could be suicidal, be aware, and act accordingly, that easy access to a firearm is a risk factor for suicide.
If your gun fails to fire, or sounds weak when you pull the trigger, keep the barrel pointed in a safe direction. This can be a delayed ignition, or a squib. Both are extremely dangerous. After two minutes (longer if you don't have a clock, and are just counting it out), you can open the chamber, remove the cartridge, and ensure that the barrel is free of obstructions. Depending on the kind of gun, this may be by running a bore rope through, or by looking from the chamber end of the barrel through towards the muzzle. If the barrel is obstructed, take it to a professional without firing it again.. If this happens more than one time, throw out your ammo, find a new ammo supplier, and make sure that your ammo is exposed to minimal moisture in storage.
Finally, the axioms of gun safety:
Treat every gun as if it is loaded. Even when you have checked, continue to practice safe handling.
Never point a gun at something you are unwilling to destroy.
Know your target, and what is behind your target.
Keep your finger off the trigger until you are ready to fire.