All of this soup has quickly depleted my stash of stock, but fortunately, I was prepared. Store-bought stock is fine and all, and I'm no stranger to flavored bullion, but they are a bit expensive, and the salt content is a bit of a deterrent. Stock is really just brown liquid that is made from unsellable vegetables and is slightly more interesting than water. That said, I don't bother buying it.
Instead, I keep a 7-cup plastic bin and lid in the freezer and I store scraps there. Tops, stems, peelings, and things that have gone a bit too dry or a bit too soft to be very interesting all go in the bin. I also put the whole onions left over from cooking black beans and celery that I intend to eat as a healthy snack and never do in there.
My most recent batch happened to make a perfect 8 cups, but usually I have a bit left over. I just put the even amount in a small ice cube tray I got at the dollar store. Conveniently, the compartments are a perfect, star-shaped 1 tablespoon. When those are frozen, I pop them out and store them in a baggie in the freezer and then I have them for those infuriating recipes that call for a tablespoon of broth or wine. No one wants to open a box for so little, and sometimes you just finished that last tablespoon of wine.
Generally I'd say that the flavor is not as strong as the store-bought stuff, but stock is usually just intended as a non-offensive liquid base. So it works well for me to have a mild stock that can be functional without doing much to the flavor of dish.
Plenty of cookbooks have recipes for stock, and I've made a few versions. Maybe my palate is just too barbaric, but I can't tell tell the difference between official stock and thrown-together-from-scraps stock. Since I can't, I go with the cheaper one.
It might seem like a small thing, but reusing those veggie scraps does save you money, and it does reduce the amount of material that you're tossing into a plastic bag that will go into a landfill.
If you want double points, you can compost the leftover vegetable goo. If you're not equipped for that, just celebrate squeezing every last bit from food you bought with money and eat your soup.
Don't forget to reuse your plastic bags! I've included this helpful reminder cat pointing at you, since stock is not very photogenic.