Shopping for food

Hi everyone
I'm on step three of the program but I'm a bad organizer and usually run out of food to prepare my balanced meals and when this happen I eat whatever is in the house and feels sick for days.

But I'm also afraid to buy more than I need because of my budget and food spoiling
Do you have tips on shopping for a week worth of food to make sure you always have your pantry and fridge full? What you shopping list is like?

thank you