My niece who has recently (this week) gone vegan asked me what staples she needs to keep in her pantry for vegetarian/vegan cooking.  Here's my list of things I cannot be without.

Spinach - prewashed, organic, ready-to-go for recipes or salads
lettuce
tomatoes
onions
baby carrots
lemons (1 or 2)
mushrooms - always great to have on hand, but don't overbuy since they don't last long
potatoes
fresh fruit - choose your favorites, two or three types
dried fruit - raisins, cranberries & dates are my favorites
sunflower seeds
nuts - walnuts, pecans, almonds - pick your favorite
Brown Basmati rice
white rice
oatmeal
vegetable broth
canned diced tomatoes
canned organic beans - black, garbanzo, kidney
marinara sauce
dried pasta (I use gluten-free.)
garlic bulbs
basil
cinnamon
salt
black peppercorns in a peppermill
tamari (gluten-free soy sauce)
Thai garlic chile sauce - only if you like hot food
honey
baking mix - Bisquick makes a gluten-free mix almost as good as the original.
sugar, agave, or stevia - however you sweeten
assorted teas
frozen vegetables - assorted including vegetable blends
olive oil - extra virgin
red wine vinegar
balsamic vinegar
white vinegar
AND DAIRY PRODUCTS I WOULD NOT BE WITHOUT, BUT YOU CAN FIND VEGAN SUBSTITUTES:
butter
sour cream
2 % milk
yogurt - plain, Greek, organic
sharp cheddar cheese
mozzarella cheese

From this pantry list, I can make a variety of meals that are quick and easy.  These are also basic ingredients that are combined with other ingredients to make more complicated meals.