I go almost every day. It's a good reason to get out and go for a walk.
What I buy mostly depends on prices/discounts. And only what I can carry in my backpack. Potatoes when affordable, otherwise rice; frozen veggies, ham/cheese, bubbly water, beer.
Potatoes are more expensive than rice in the Netherlands?
Edit: just did the math for my German prices and they seem about equal. I always thought rice was a bit more expensive.
Edit 2: just realized that it's easier and cheaper to prepare a meal with potatoes for me. I'm cool with plain mashed potatoes or simple pan fried potatoes (about 50c of extra ingredients each) but for rice I need something to go with it, which is gonna be more expensive than what I need for potatoes