During the week, I live alone, and in the weekend, I live at home, so my mom gives me money to come around every week, of which I use a pretty big part to buy weed. I don't really budget, but my rule I kinda follow is a gram a day, which seems healthy to me.
I also get smoked out a lot (for which I'm ever so grateful), but since I don't pay for that, it doesn't count