I have favorite pantry staples, frozen vegetables & meat (at least grilled chicken strips) we keep stocked.

What about sweet potato, winter squash, or pumpkin for thickening? 

Several years ago we started using a large 'insta-pot' type pressure cooker for soup.  Found we could get the same rich flavor with less prep, got rid of any added fat & less cook time.  Great flavor without sauteing or browning (but it is an option).  Two cups of broth (or water) is minimum for cooking - I usually get Kevin to start with 4 cups for soup, because more broth can be added later, concentrated portions takes up less room in the freezer. 

After trying different store-bought broths/stocks, we always keep our favorite cartons of chicken, vegetable & beef on hand (canned beef au jus can be added for extra rich flavor).  I keep 'Orrington Farms' powdered soup bases to add a little extra flavor & use in place of plain salt.  I believe broths & stocks infuse flavor - where water removes it. 

I like having a small jar of chopped pimento and larger jar of roasted red, or yellow peppers on hand.  Also, canned stewed & diced tomatoes, some canned white & kidney beans, some dry noodles, rice & barley.  Sometimes we can't get good fresh ginger, or garlic - I'll keep paste form in the fridge.  My favorite freeze-dried herbs to keep on hand (singles & blends): Litehouse brand (easiest to order on Amazon).

My 1st rule of thumb to start just about any soup (besides broth/stock): however big the onion I use, use at least an equal amount of carrot & celery.   

If you use meat & vegetables you like, you really can't go wrong.  I've even thrown in a bag of shredded cabbage slaw mix in a hurry! 

Dump in any combination of frozen (or fresh) meat & vegetables + herbs and any spices.  Any thickening is done at the end (for something needing cheese, it's the very last).  For any cream soup I'll use some canned evaporated milk at the end (with flour if it needs thickening).  Don't need to worry about boiling or problems with citrus using evaporated milk... great lower fat sub for cream (it's a pantry staple). 

Worse case scenario, I'll adjust with a little something tart/acidic or sweet at the end.  A touch of ground corriander or nutmeg for poultry, some ground alspice or mushroom powder for beef, etc...  A little fresh, or dried fruit (or citrus) for sweetness/acidity in savory soups - works great.  Raspberries (my fav with salsa), mango, tart apple, dried tart cherries, pear (hey, with the winter squash, or pumpkin soup).  A touch of tart apple cider can add acidity (and I do LOVE Pearl River Bridge Chinese Black Vinegar for cooking).  Consider a touch of a liqueur, wine, sherry, vermouth, or even beer.

One of my favorite soups is Wonton 'on steroids' - 4 cups chicken broth/stock, sliced bunch of bok choy (greens, too), bag of frozen potstickers (we like pork), plus a 2 teaspoons 'each' of: frozen orange juice concentrate, black or rice wine vinegar, sweet chili sauce, and fresh grated ginger.  My pressure cooker takes a few minutes (10?) to pressurize - cooks 8 minutes on high pressure!  Release the pressure & add 2 to 4 more cups of broth/stock.  Garnish with sliced green onion.