How could any of us know what the "average" person spends? Even if someone could, in the end you need to base a budget on your needs. And no one can definitively say that you can eat for no more than $X and be satisfied without knowing you.

If you are sort of person who can (and is willing to) get by with a bowl of oatmeal for breakfast, a small sandwich for lunch and some boiled rice and beans for dinner, then your food costs will likely be lower than someone who needs and/or wants something more and/or different.

Personally, I am all over the place. One day my food expenses may be relatively low. The next day, I may drop $50 on a steak dinner out, plus breakfast, lunch and snack costs. If I had to guestimate, I would say I spend a minimum of $15-$20/day for breakfast, lunch, dinner and snacks, not including adult beverages.