This is mostly an ad-dependent thing, so there's no way to give a definitive number.
I'm making about $2 a day right now on weekdays (I barely make a cent on weekends because I don't update then) and I find I make those $2 when I get between 1600-2500 views in a day. I made $1 on the weekend from getting 622 views on Saturday and 248 views on Sunday (that's pretty dead considering the weekday views lol) combined, which matches up with earlier data, so for now, it seems you need to get at -least- between 800-1000 views to get a dollar, and that's a generous guess just from looking at a stats page. It definitely depends on what ads are on your page as well, though, which is something you can't control.