By far the most useful herb for me is parsley.
I use it on and in many of the dishes I prepare and especially if I am putting it on Recipe Yum, as that small piece of parsley just gives the photo a slightly better look.
I also really like parsley and often chop up a lot with chopped tomatoes -parsley goes with just about everything, and so I have it growing in several places.
I also use garlic chives which I have had growing for years however now it is start to not re-generate as it used to, so will probably re plant.
I also have coriander growing almost wild everywhere. I use coriander in quite a few dishes also. This keeps coming up year after year and I have many seeds I have taken from them which I also plant all the time.
Most other herbs I do not use a lot of so just buy as I need them.