Mix whatever you prefer (something sweet, salty, sour and some olive oil), and pour some olive oil on top to create a layer of film. This will block oxygen from oxidizing some ingredients and it can be kept outside of fridge for a week easily (probably won't have the chance to last this long anyway). Shake before use and top up oil on top after using. Same goes for sorting larger batches of pesto - make it flat and cover with oil.