OK, so we've seen some recommendations going around for people who want to buy their first firearm w/ the $600 check. First thing to know, pistols are terrible firearms for beginners, creating barriers to learning and more chances of a negligent discharge than with a long arm.
We break firearms into 3 categories: primary arms (the I can only have one category), secondary arms (I want to provide food for my friends/family, & tertiary arms (the specialized weapons that require lots of training, i.e. handguns & precision rifles). https://iaf-fai.org/2020/09/26/skills-for-revolutionary-survival-4-primary-firearms/
"Handguns can best be described as a last ditch defensive firearm. What they are designed for is close encounters, any further (as cops in NYC have regularly demonstrated) you run severe risk of errant bullets hitting innocent people." https://iaf-fai.org/2020/12/06/tertiary-firearms/
If you want one gun for revolutionary purposes/defense, get an AR or Pistol Caliber Carbine. If you are on an extremely tight budget or want to get used to the fundamentals of marksmanship & firearms safety, don't get an AR/pistol. Get a 22 Long Rifle or a Pistol Caliber Carbine.
For our extensive list of firearms, check out the lists in the articles above. Also look on the used market; find a Ruger 10/22, High Point Carbine, or KelTec Sub-2000 for under $300. Use the rest for ammo. Most gun shops will give you a free gun lock, so be sure to pick one up.
Secondary firearms that covers rimfire practice rifles and shotguns can be found here. Stay safe, always act as though your gun is loaded, never point your gun at something that you are not ok with shooting, lock your gun around kids/alcohol, & practice! https://iaf-fai.org/2020/11/11/skills-for-revolutionary-survival-6-secondary-firearms/
Here's a good deal as of today, with ammo still available: https://www.sportsmans.com/shooting-gear-gun-supplies/shotguns/maverick-arms-88-field-and-security-combo-shotgun/p/1506620
Here's a good deal on a 22 (though check walmart as they usually have the lowest prices without shipping needed). https://www.kygunco.com/Product/View?ItemNo=146973