You'll get better no matter how much you practice. You'll get better faster if you practice more (and are practicing the moves correctly).
I've only been flourishing seriously for a month or so now.
I play with cards while reading topics here, watching tv, while my girlfriend reads at night and I also set aside time to practice as well.
couple hours a day?...I'm not sure, at least 2 probably up to 5.
I have seen a lot of improvement.
45 mins. of dedicated practice a day is a good start, if you keep that up and then also carry cards and practice every chance you get, then you'll probably log at least a an hour and a half a day.
You'll also find that practice becomes more productive the more you work on a flourish, because you drop cards less often.
Hope that helps.
-Rik