Trying to find the "right" amount for groceries each month.

I struggle each month with knowing how much to budget for groceries. I don't have a good sense for whether I am budgeting too much. Take this month for instance. June has four weeks and I budgeted $250 for the month, which strikes me as being too much. However, the first two weeks of the month have looked like this when it comes to groceries:

Week 1
$10.22 - produce stand
$38.71 - Safeway

Week 2
$17.93 - produce stand
$60.54 - Safeway (this included household cleaners)

I also have a "misc" food category in my budget to allow for things like snacks I pick up outside of regular grocery shopping trips. I really starting to think that I need to cut this category out. I put aside $50/month for this and wonder if I really should be. I'm already over in that category for the month of June. I think it would be better for my budget and for my waistline if I cut this category out and allowed less snacking.

On top of this I have a category for Costco, which has $50 per month in it. I'm not really sure why I have this as it's own category. I need to give this some thought and determine whether or not it should be eliminated.

I also wonder if things like household cleaning supplies need to be taken out of the grocery budget line and put into their own category. I do have a "household items" category and the rice cooker I just bought on sale falls in this category.

This week begins week 3 and I intend to spend approx. $40 on groceries as there are not that many things I need to pick up. I do need fresh fruits and veggies and some lunch fixings for taking with me to the office. I have enough food on hand to make dinners.