In terms of quantity, the spice I use the most is paprika. I try to cook Hungarian at least once a week, and many recipes begin with onions, fat (lard or other animal fat if I have it around), and paprika. Also, I use it a lot for other cuisines, like as part of the red pepper mixture in my chili spices, in my rubs for roasts and barbecue, in my cajun spice mix, etc. By far, it is the spice that I use the most and need to replenish most often.
Next would be simple black pepper (although I usually have a couple different varieties of black pepper around). Very few dishes I make do not contain black pepper.
Beyond that, and including dried herbs in my spice cabinet, in rough order I would say cumin, allspice, nutmeg or mace, Mexican oregano, cloves, marjoram, caraway seed, coriander, then Mediterranean (regular) oregano. And there’s a lot more past that, but those would be my most used.
In terms of fresh herbs, cilantro is number one, followed by parsley, basil, rosemary, thyme, dill, tarragon. A lot of these are limited by availablity at the grocery store if (like right now), it’s out-of-season (i.e., not available from my garden). Also, cost. Cilantro and parsley are fairly cheap, usually $1 for a couple bunches, but my grocery has basil and the like in those plastic containers for something like $2 a small handful. I typically only use fresh basil when it’s out of my backyard for that reason, as a lot of my basil recipes require a LOT of basil. There are some groceries farther afield that have more reasonable loose herb prices, but when I’m cooking from the neighborhood, I have to limit my fresh basil usage to when I have some available from my garden.