QueSera's list is good
I bulk buy a lot of my food online (and am a closet prepper!), my pantry has large stores of: dried pasta, rice, quinoa, polenta, oats, lentils, beans, chickpeas, cashews, almonds, tins of chopped tomatoes, coconut milk, and more beans, jars of gherkins, olives, sun dried tomatoes, sauerkraut, kimchi, roasted peppers. Bottles of different vinegars, oils, thinks like Worcester sauce, hot sauce etc. Tubs of nutritional yeast, smaller quantities of lots of other stuff: other nuts (Brazil nuts, hazelnuts, walnuts, peanuts, pine nuts) seeds (pumpkin, sunflower, chia, hemp hearts, flax), tonnes of different herbs and spices, dried fruits, random things like kelp powder, spirulina, cacao powder/nibs, dates.
Fresh things that I buy most often, apart from fresh fruit and veg, are non-dairy milks/cheeses and tofu - all of which are easy enough to make from scratch to be honest. Some specialist ingredients to get hold of make it easier - lecithin, nigari, agar agar, vital wheat gluten as mentioned up thread. I have just started exploring making things from scratch with this book and it's been amazing so far - fantastic pancakes, macaroni cheese mix and non-dairy milks so far. I have a kg of soy beans waiting to have a bash at my first homemade tofu soon!