If you can, get a box of each brand and loading of ammo, from several retailers. Try them all out. Have a notebook nearby.
What you are looking for is that mix of bullet weight and powder burn that works best in your Glock in your hand, and the distances you would like to shoot at. Typical "ball" ammo (meaning jacketed solid core, not hollow-points or soft-points) in 9mm will weigh in at 115-grains per bullet. Some shooters prefer 124-grain bullets, but these cost more. Try them all, see what is most accurate for you, for the price of ammo. Make notes as you are shooting, and after cleaning your Glock, review your notes and you might find the answer right there.
Remember, though: stay away from bare lead ammunition....your Glock won't like it
