I don't have a lot of stuff sitting around in my pantry. I don't even have a lot of room for extra stuff, but there are some things I try to keep on hand in small quantities.
I read a book on hospitality once where a family kept an entire closet and fridge full of kid friendly junk foods, to help draw they neighborhood kids to their home with their own children as primary hosts. I loved the idea, but the reality of an introvert living that lifestyle is a little slim. I would instead say to introverts, your regular guests that drop by on occasion can have a special treat on your shelf. If you're super organized, you can keep a journal/folder of friends favorites and purchase one or two before they come over.
My main thing I would encourage you to have is coffee and tea fixin's. Keep not just sugar in the sugar bowl, but a couple packets of pink, yellow, and blue if you can find them. Have dry creamer for emergencies and cream around if you know folks are coming. If you don't drink coffee, that's okay. Keep the makings of hot tea around instead. A box of Lipton will do the job nicely. Just brew directly in the cup.
Most folks are not tea snobs. You will occasionally run into one, but they are a gracious bunch and will choke down even the worst cup of tea, because they know it's about the company more than the beverage. I'm not sure if the same is true for coffee snobs. Most of those will prefer to not drink than to drink instant. I would say in this realm, if you are unwilling to drink the coffee you make, then just do without.
Why warm beverages instead of keeping cold ones? You can keep cold ones, that's fine. Warm beverages take time to make and they let the person know that they're worth the time. So don't rush these things, put a pot on to boil instead of popping it in the microwave. Sit down and wait with one another. It teaches us so much to wait.
Here's a little secret weapon I have to share. Fresh baked cookies, ready in about 15 minutes. Granted it takes more time to prep, but totally worth it. Mix up a batch of your favorite drop cookie. Chocolate chip, peanut butter, oatmeal, your choice. Bake about a dozen, you deserve some tasty goodness for your labors. Now, take a piece of wax paper, Saran Wrap or parchment and put it on a baking sheet and drop the remaining cookie dough on the sheet. They can be right next to each other, generally a batch will fit on one sheet. Now place this in the freezer for an hour or so. Once they've hardened, peel them off the sheet and store in s freezer ziplock bag. When you're ready for fresh cookies, pull a few out and back as usual, adding a few minutes onto the baking time. Easy peasy. Fresh baked cookies in minutes. And raw cookie dough to taunt you for days. These don't stay tasty forever, stupid freezer burn, so bake them off and make a new batch every few months.
That's it, that's my suggestion, keep things for how other people take their coffee and have cookies as a staple in your freezer. Who wouldn't say yes to hanging out and sharing some cookies and coffee?