I have a constantly changing palette, and am learning to refine it more each day, so feel free to agree or disagree with my current must-have spices. After all, these are simply my personal faves. Without further ado, let's get down to business.
1. Garlic Powder
Now listen, I know garlic is not the most out there spice, but it definitely takes things up a notch and can pair with anything. Shrimp, chicken, veggies, even eggs, I guarantee it's going to taste better with some garlic sprinkled on it. My advice is to use generously (I don't even measure it out), but make sure you add early on in the cooking, so that the full flavor of the spice can be absorbed by the dish. Probably my top must-have.
2. Crushed Red Pepper
Yes, crushed red pepper like the kind you receive in little packets when you order from Pizza Hut. While it definitely pairs well raw with pizza, it's also delicious to actually cook with as well. One of my favorite things to do is throw some into a pasta sauce to give it a little heat. Crushed red pepper also tastes magnificent with an omelet. Basically, use this with anything that you want to make mildly spicy, but without using a spice with a strong flavor that will overtake the dish.
3. Ground Thyme
This is a spice with a very mild, earthy, and fresh flavor. I use it pretty heavily in any soup that I make, but I also hear it goes great with pork (I don't actually eat pork, so I wouldn't know). I think this is a must-have spice that probably gets overlooked, but it definitely makes my list of must-haves. If you have a soup dish or veggies that you think are missing something that you can't quite place, try adding some thyme.
4. Freeze-Dried Chives
Chives are a newer addition to my spice cabinet, but much like garlic, I've grown to use them in almost everything. For those who may not know, according to this handy comparison, chives are related to scallion onions. Flavor-wise, chives have a mild onion-y flavor, while the onion flavor of scallions is more rich and robust. I recommend freeze-dried chives over scallions because there is no prep required. (Pro-tip: chives should be eaten raw, as cooking them can make them lose their flavor. Something I didn't know the first couple of times I tried cooking with them).
5. Ground Cumin
This is a spice I've been accustomed with since I was a kid, thanks to my mom's delicious fideo, of which cumin is a prime ingredient. I would describe this as yet another earthy spice, one that resembles a more mild chili powder. Personally, I like this spice best with beef dishes (think tacos or steak), but it would also taste wonderful with soup, stew, or anything that you want to have a more hearty, savory edge to it.
This is just a basic list to get you started and thinking about what kinds of spices and flavors you'd like to experiment with in the kitchen. If you want to continue on this spicy, adventurous journey, try checking out this article about making your own spice mixes. Google is your friend in this regard as well. Happy cooking!