Look into marinades and brines. You can add a lot of flavor with minimal calories. Also for sauces you can make a reduction out of a stock(broth), whether it is a chicken, beef or a fish stock. just start reducing it down on the stove. You will get all the flavors concentrated into a nice syrupy sauce. Just don’t reduce it to far or it will be to salty.
I am a professional chef and these are some of the things that I do at my restaurant.