Every single person is different. Some people may be comfortable after 50, some 100, some 300, some even more than that. It's until you feel comfortable shooting the gun.
In my opinion, you shouldn't be looking for mechanical flaws with the firearm, you may shoot 5000 rounds at the range without a problem, and then need it for self defense and it doesn't fire the first round in the chamber.
Instead, I think you should be getting used to shooting the gun. Get used to the sights, some guns you need to aim a bit lower than your target to hit it. The goal should be to get as accurate as possible with it.
But also, I would carry it after the first time at the range simply because if it's your only gun for CC, it's better than no gun at all if you need one.