You mention not costing a lot. How much can you spend? keep in mind you will need to purchase ammunition (which in the current political climate is in short supply and high demand = high prices), some form of hearing protection and a cleaning kit for the gun.
Good German firearms such as the Sigs, H&K, and Walther are expensive new and typically retail over $400.00 on the used market in good condition.
You will get a hundred different answers to what is best, but 38 Special and 9mm Luger are good starting points for self defense. Both have decent stopping power and recoil that is easy to handle even for newbies. Also both don't have the harsh report or fierce muzzle flash of the magnums
For new shooter that wants a self defense handgun on a budget, a 357 medium sized revolver from one of the major makers is
hard to beat. They are simple, robust, and offer most bang for the buck. You can find used Smith & Wesson Model 19's, Ruger Security Sixes for reasonable prices and Taurus revolvers that can be bought brand new for under $400.00. The neat thing about the magnums revolvers is you can shoot 38 specials as well as 357 magnum ammunition, so if you decide you want to work your way up to a magnum load you already have the gun.
If you're heart is on a semi-auto, you can find used Ruger P series 9 mm's for just around $400.00. I haven't priced them, but some of theused polymer frame pistols such Smith & Wesson Sigma and Glock might be had for under $500.00.