I use mostly Greek yogurt, but I do add a small scoop of mayo for best texture (because yogurt separates; it's probably 1-2T per 1 1/2 cups of yogurt). The rest is a squirt of dijon mustard (about 1 t), onion and garlic powders (1t and 1/4 t respectively), parsley (1T), thyme (a pinch), 1T of apple cider vinegar, salt, and pepper. Chives can stand in for the parsley, and coriander for the thyme if I need to. Sometimes I add some paprika, sometimes not. I mix it all in a wide-mouth mason jar. It's pretty thick, so you may want to thin it out if using it as salad dressing instead of dip.
My measurements tend to be approximate.