No doubt the best first handgun!Glock 19. Affordable. Compact yet large enough for OC. 9mm is cheap and easy to learn on and glocks are the same. You're getting the reliability of a gun twice as much on a platform that anyone can use.
If I had to say one without knowing any of the answers to the questions I posed I would say a Glock 19. I recently picked one up after having tried several makes and models. I have never been a fan of the way Glocks look but here is what factored into my decision.
Reliable
Easy to clean and work on
Tons of accessories
Cheap accessories
Cheap magazines (I hate guns that have $40-$50 magazine prices)
Proven longevity
Police departments all over the world count on them
If you could pick. It can be any...
Caliber
Brand
Color
Length
Any accessories
If money is a consideration, it's hard to beat a Ruger P95