I have quite a few suggestions.
I get tired of hearing everyone always answer with get training. Not a bad idea (actually a great idea) but still doesn't answer your question.
If you have to have a carry gun right now and dont have much experience with handguns and you are worried about safetys/double action for safety I suggest just go ahead and get a snub nose revolver. I will probably have a few people jump on this and say revolvers are awful defensive weapons, they are wrong, revolvers are great and reliable, they shoot when you pull the trigger and are a safe and reliable carry option. most defensive uses for a handgun are within watergun distance, what I mean by that is they most often happen within a distance that you could hit them with a water gun if thats all you had. in that situation the snub nose revolver would be perfect. I would couple the revolver with a good ruger mark iii to get your shooting fundamentals down.
here are some revolvers in the $200ish range:
http://www.slickguns.com/product/ta...volver-2in-5-round-blue-21783-w-taurus-rebate
http://www.slickguns.com/product/ar...blued-alloy-frame-wood-grips-fixed-sights-219
heres a ruger .22LR:
http://www.sportsmansoutdoorsuperst...ruger-2245-mark-iii-target-22lr-molded-5.5-in
The .22 is cheap to shoot and extremely accurate which would allow a lot more shots down range and get you some great practice.
Next suggestion is a sig p250:
A compact hammer fired 9mm with a double action trigger only, made by sig, extremely accurate, and under $500. Great choice for a carry gun and a great shooter. its bigger than you originally posted about but with an alien gear holster($35) it should conceal quite well.
Next would be a smith and wesson shield:
GREAT carry gun, not a great range gun for many reasons other people have already covered. comes with either a safety or not whichever you prefer! Get it if you a determined to get a single stack 9.
last suggestion would be a glock 19 because its the do everything gun, I carry it daily and love it, also the smith and wesson sd9ve is a great budget alternative to the glock 19.
Ok the glock isn't the last suggestion. Sig sp2022, polymer DA/SA hammer fired sig. easily found for under $500.