Rinse and spin dry arugula and fresh mint. Remove any long stems and set mint aside for later. Tear or coarsely chop arugula (unless you’re using baby arugula). Place in a large bowl.
Peel cucumber and remove seeds if desired. Cut into chunks (whatever size you prefer). Add to bowl.
Cut mint into julienne strips, then slice across. Dice avocado. Add both to bowl and toss lightly.
Drizzle oil and lemon juice over salad and season with salt and pepper, to taste. Toss again and serve.