I have. I own and shoot a few handguns in real life - not first person shooter games -
9 mm Luger, 40 S&W. 22lr, 380 ACP, and 45 ACP. I may have a tad more hands on experience than May 2017 (June 1978), and would not be so eager to make a nonsense blanket statement about a specific calibre being suited only for target practice, especially when the Beretta M9 in 9 mm Parabellum was the designated sidearm of the US Military for over 30 years, and was recently replaced by a modular sidearm in 3 caliber, non of which was 45 ACP.
So for my 2 cents, for the OP, 22 lr is a good starting point, see if you can handle some different guns that feel right for you, take everything here with a grain of salt, sift through some of the good advice others have posted above, and buy the one that fits and feels right. Start smaller, avoid developing a flinch by choosing too large a calibre at first and above all have fun experiences. Proper technique and regular practice outweighs caliber.
Going out to shoot a few magazines now. Don't own any "clips".