Since I am just getting going in my location my percent is not accurate, this spring I will keep records and have a pretty good idea of where I stand. It's hard also because I am focusing on establishing herbs, so they make up a very small percent of diet anyway. Some plants that gave the most bang for the buck in the half season I've had here are:
Radishes - these are so easy to grow, delicious and pretty much daily I would pick radish greens. so it's a 2 for 1 plant.
Chard - I grow a chard that has big leaves and a stem like celery, leaves are great raw, the celery looking stock is great added to soups or other roasted veggies also a 2 for 1 plant
Broccoli - since I knew I only had half a season I grew broccoli for its leaves, great for salad
Nasturtium - another daily picked green that is a nice change of flavor
Black nightshade - after ample research into this plant I made cooked greens of it and it had an excellent flavor, also ate my fill of its small berries. I gave the entire plant to the
chickens when I was sick of it taking up garden space and they loved love loved it. So it's a 3 for 1
Arugula - I planted a huge amount of Arugula, and had more than I needed. I thought more would go to seed, but only a few plants did, the others remained edible all the way up until frost killed it. Mature arugula is uncommon commercially in my
experience, and I can see why, the flavor is very serious, accents nasturtium well.
Lambsquarter - another one that gave ample spinach tasting greens, and a boatload of seeds. I harvested the seeds this year for planting next, and gave the leftovers to the
chickens. Next time I am going to use the seeds like you would quinoa.