Put a couple chicken breasts in ziploc bag and pour in some salad dressing and let hang out and marinate. If you don’t have time to let it marinate a bit, then just season breasts with Greek seasonings (try Cavenders All Purpose Greek Seasoning).
Cut tomatoes in half or quarters. Peel and seed cucumber (if desired) and dice in chunks equal size as the tomatoes. Dice or slice red onion. Combine in bowl with some red wine vinegar (about 1/4 c.), dill, salt & pepper to taste.
Grill chicken on the BBQ, then slice. Heat tortilla, fill with some chicken, tomato/cucumber mixture, add a bit of tzatziki sauce and feta to taste.