When I have money, 500-1000 rnds a go.
When I don't have much money, a box or two over the counter.
The important thing is to stay in the habit of adding to the pile on a regular basis. And when I'm buying 'small', I'll take a chance and try a different brand or loading to try out---or buy a box for one of my seldom used guns (ie. my .32 ACP).