My first (and slightly snarky) response is "anything in 9mm!"
However, I realize you are asking a sincere question. So, here's my more sincere reply.
The Glock 19 is a very robust pistol and will shoot almost any 9mm (9mm Luger) loads. They like jacketed ammo. Some people say not to use lead bullets because of the design of the rifling. Others have successfully shot thousands of rounds of lead ammo. The G19 will also eat up hollow point defensive ammo with ease.
Try a few brands and decide what you like to shoot and what meets your needs for the gun's intended purpose and your budget. This is not a picky firearm!
For personal defense I agree with 124 grain bonded hollow point. I seem to have good luck in all of my 9's with Speer Gold Dot 124. Just every day at the range I have decent luck with blazer brass ....read cheap!!!!
Really?...guess those 1k rounds of ultramax lead rounds I've shot out of my G19 where only a figment of my imagination....and I guess having zero issues with running them was also a part of my imagination.