You need a shelf of magic ingredients. The missing Oooph in food is usually salt, sour, sugar or fat plus umami.
Soy sauce light and dark, mushroom ketchup, Worcestershire sauce, fish sauce, balsamic vinegar, dry sherry, dry vermouth, red wine, hedgerow jelly (made with hawthorns and anything else you find) redcurrant jelly will do, extra virgin olive oil, ghee, sesame oil, pontack sauce, lemon juice, lime juice, miso, dried lovage (it is in Maggi), grow fresh herbs in the garden, paprika (sweet, smoked and hot), good old vinegar and salt. Ketchup and brown sauce work just fine.
Most of all you have to ask yourself when tasting "What is this missing?" and look back at the list : salt, sour, sugar or fat plus umami.