Glocks are not, in my opinion, easy guns to shoot.
There are two types of triggers that lend themselves to natural accuracy, and selecting between them is mostly a matter of personal preference. The first type is the classic “glass rod” trigger – short and light takeup, crisp break, and very little overtravel. This type of trigger is normally represented in the 1911-pattern gun. The second type of trigger is often described as a “rolling break” – constant weight across the full trigger travel, indistinct break, and lots of overtravel. This type of trigger is commonly found in old DAO revolvers, and the new Caracal pistol has an excellent example of a rolling break.
Glocks have neither type of trigger; a typical Glock trigger has a fairly heavy takeup, a distinct break, and lots of overtravel. This makes the Glock very sensitive to trigger finger position. A little bit too much/too little trigger finger, and you start getting wide shots left and right.
So what to do? Well, you can try removing some of the overtravel from your trigger. Lone Wolf Distributing sells a Glock trigger housing with an overtravel screw installed, or you could try a Ghost Rocket connector. I’ve tried both, with limited success.
You can also play with you trigger finger position, to ensure that you are moving the trigger straight to the rear. I’ve found that I need to use only the barest tip of my finger to press the trigger. Others have reported that they pull the trigger with the crease of the first knuckle.
When you dryfire, keep an eye on how the front sight moves. Any significant lateral movement during dryfire means the trigger is bearing to one side during the overtravel. Try doing twenty reps of a perfect trigger press with your normal finger position, twenty reps with a lot more finger, and twenty reps with a lot less finger. See which finger position yields the least sight movement. A laser sight can be really useful for this drill, as it makes lateral shake at the muzzle very easy to see.