Most spice cabinets are graveyards: half-empty jars of paprika from three years ago, a mystery powder that might be cumin or coriander, and approximately seventeen varieties of something called "Italian Seasoning." Building a spice cabinet you will actually cook from requires a different approach -- starting with fewer, better spices and understanding how to use them before buying more.
The single biggest mistake people make with spices is buying too many at once. A trip to a specialty shop results in twelve new jars, and then they sit unused because you do not have the repertoire to deploy them naturally. Instead, build your cabinet around a core eight: kosher salt, black pepper, cumin, coriander, smoked paprika, chili flakes, turmeric, and cinnamon. These eight cover an enormous range of cuisines and dishes. From these eight you can make a simple taco seasoning, a Moroccan-inflected stew, an Indian-spiced lentil soup, and a Greek-style marinade. Master these before adding anything else. When you do expand, add spices to solve specific problems. Buying sumac because a recipe called for it and you have no idea what else to do with it? That jar will die unused. Buying sumac because you loved the brightness it added to that fattoush and you want to use it on roasted chicken, in salad dressings, and on hummus? That jar will empty within a month. Whole spices last two to three times longer than ground, and toasting them briefly in a dry pan before grinding unlocks flavor compounds that pre-ground spices have already lost.