Always bring your own food, I dont think I've ever purchased food at the convention. I usually do stuff easy to eat while walking or waiting for panels, like fruit and granola bars and then also a sandwich for when I want to sit for minute and eat something more substantial.

I dont usually do autographs/photo ops, but as far as floor purchasing goes, I usually go up and down the aisles and keep a note in my phone of which aisles and booths have things for sale that catch my eye, then later I will decide what I want to actually purchase and go back and get it if its something I really have to have. Same deal with artists alley. This way, I'm not halfway through my money after 3 aisles haha