I like my sauces and gravies thick. They should easily coat a spoon. There are lots of ways to thicken up a sauce or gravy. Arrowroot, baking soda, corn starch, flour, etc. But they all involve a bit of chemistry and they need to mix with something (like butter or water) before you use them.
I found the easiest way to thicken a sauce or gravy is to use potato buds. Just pour them in and stir until you get your desired thickness. There's no pre-mixing...they go right into the sauce or gravy. They are neutral in taste, so they do not alter the flavor. This is an item that no pantry should be without.