For me it depends on how you play, if you're going for a very attacking style and plan to get 20-25 shots a game at least then expect upwards of 6-7. I've switched back to a more possession type and I don't usually get more than 3 a game unless a real chance from range pops up.
I would be worried if you were getting into double figures though in any style, unless you were getting near 40 shots in a game.