Smarter Gun,As a general rule (Based on the experience of most shooters) 250-300 rounds is the minimum amount to use for a function and reliability test. Personally I like to run, at least, 500 rounds through a gun before I'm comfortable with carrying it. A caveat is to be sure to use FACTORY AMMO during all function testing. The brands to use, of late, seem to be Speer, Winchester, Remington, and - for a GLOCK - CCI Blazer.
I know the parent company is the same as two of the brands mentioned above; but, some scary things have been reported about Federal ammunition, lately; and I, for one, have been staying away from the Federal stuff.
If price is an issue, Sellier & Bellot and Wolf are acceptable to use; and, personally speaking, I've been impressed with recent purchases of, both, Fiocchi and PMC pistol ammunition. 'Wally-World' has their Winchester, 'white-box' ammo specials. This stuff shoots reliably, and isn't too dirty; but, by the time you're finished, you'll be left with the overall impression that you haven't been shooting high class ammo! (You'll be right, too.)
I recently completed a 400 round qualification course using Fiocchi 45acp hardball. Not a hiccup, and very clean. For your information I use the big three: Speer, 'Gold Dot', Remington, 'Golden Sabre', and Winchester, 'Silvertips' in my carry guns. I wish that Winchester, 'Black Talons' were still available; I can't see any good reason, 'Why' this excellent combat ammunition was pulled from the shelves. (More stupid mass-media hysteria, I think!)
The important point to make, here, is to be sure to, 'wring the gun out' before you start to carry it. Good for you to have asked this question!