Drain and rinse the chickpeas and dump into a large bowl. Add the torn olives, capers, and torn parsley and mix to combine. Dress the salad with the olive oil, vinegar, salt, and pepper. Then add in the crumbled feta cheese and toss again.
If you're serving the whole thing at once, toss in the 4 cups of arugula. If you're having only individual portions over the course of a few days, mix in 1 cup of arugula to every serving of the chickpea mixture as you go, to avoid the salad getting soggy in the fridge.