The very first thing you should build should be an IFAK. Need to have a TQ and be able to stop bleeding, so take atleast a stop the bleed class.
Glock 19 is going to be the standard due to abundance of parts and they shoot good. HM are glock 17 and 43, some people prefer those especially the 43 for concealed carry. If you’re going to CC then i suggest getting a Philster Enigma, they are the best purchase you can make after buying the gun.
For rifle get an AR15. Other than legally not being able to get one, they’re is very little reason to go with something else as your first. Brand doesn’t matter too much, Palmetto State Armory is probably the lowest quality i would recommend going with but you really shouldn’t spend a crazy amount, 450 to 750 will get you something good.
After you buy your guns, throw a red dot on them get some ammo and start shooting. You’ll next want to look into holsters, slings, and other fun parts of the hobby.
IFAK is underrated advice. Unless you’re living in gangland, then statistically you’re more likely to shoot yourself than you are to shoot someone in self defense. Some community events may even offer first aid/stop the bleed classes for free. Knowing how to patch someone up will make you a better defender than a majority of American gun owners.
Should disclaim that red dot advice does not apply if you have astigmatism. TRY a red dot before you BUY a red dot. 1-8x scopes and prism sights are both valid alternatives.