Family having a stock of basics and essentials didn't happen on day one, so don't panic.
You will obviously need to get in your staple shop.
Best way to plan that is to think about your day.
Get up - need toilet paper, toothpaste and brush, soap, shampoo etc.
Breakfast - milk, tea and coffee, sugar, juice, bread, butter, cereal - add your preferences for jam, marmalade, peanut butter, Marmite, honey or whatever
What meal would you need next? and do a section for kitchen essentials such as washing up liquid, scourers, kitchen roll, cling film, tin foil, cleaning materials and cloths, stuff to do your laundry, bleach and cleaning materials for surfaces and bathroom.
Olive and vegetable oil, salt, pepper, mayo, dried pasta, rice and other stuff you just expect to go to. Plus some freezer staples. I always have onions and tinned tomatoes in and some dried herbs.
Then get yourself an 'emergency' meal plan. Baked beans, cheese and crackers, eggs. Make sure that if you're either broke or starving, there's something you can go to 