You really have to define what you want the pistol for. There’s a huge difference in wanting one for target shooting, hunting, and self-defense. Although all can do these tasks, some do it better than others. In my opinion 1911’s are ideal for target shooting, less so for self-defense unless you shoot it often, are extremely familiar with handling it under stress, etc. The traits that make it good for target shooting are also the ones that make it dangerous in untrained hands (single action, light trigger, manual safety). On the other hand the Ruger P series are decent self-defense guns but are poor target range guns.
Barrel length, size of the gun, magazine capacity (max limit of 10 but some have less), and caliber are also important considerations. In my experience the cost of the gun is minor compared to ammo cost, so get something you’ll like shooting and is going to last.
Stick with common calibers such as .22, 9mm, .40, and .45 (if you don’t reload these are usually the cheapest, and in that order).
Don’t forget to get extra magazines…you should have at least 5 extra one.
As Old4570 said…get instructions both for safety and proficiency reasons. One can develop extremely poor habits without knowing it. And poor habits can lead to serious consequences as well as poor shooting.
It’s easy to have a negligent discharge with a semi-auto (there’s no such thing as an accidental discharge unless something broke), so you need to decide if you want a SA, double-action/single-action, double-action only, etc. However safety is in the mind and actions of the shooter.
If you can’t spend more than $600 then that leaves out lots of pistols. In this range Glock’s and Springfield XD’s are reasonable choices for all-around guns. If you are using it as a house gun and range gun then I’d get a Glock 35 with a 9mm conversion barrel.
You can also get a .357 magnum revolver in your price range. Something like a Smith&Wesson L frame. This also allows you to shoot .38’s at a lower cost.
As I mentioned in the beginning, the requirements drive the purchase, especially if you will only have 1 gun.