What's more important than how much you practice is do you practice the right techniques. For instance, if your crappy grip causes you to shot low and left, the more you practice the more you ingrain the pattern of shooting low and left. If your fundamentals are sound, then practice can be expected to improve you. If you practice, practice, practice and still suck, additional practice isn't going to do you any good. You need to ID the source of the problem first.
P.S. I haven't been shooting a pistol long but I know this from golf. Same thing applies!