In a mixing bowl, combine olive oil, garlic powder, paprika, oregano, salt, and black pepper. Add the chicken thighs and coat well. Marinate for at least 15 minutes.

Preheat the grill to medium-high heat. Grill the marinated chicken for about 6-7 minutes on each side, or until fully cooked and juices run clear.

Remove from the grill and let rest for a few minutes before slicing into strips.

In a mixing bowl, combine Greek yogurt, grated cucumber, minced garlic, chopped dill, lemon juice, and salt. Mix until well combined.

Chill in the refrigerator for at least 10 minutes before serving.

Warm the pita breads on the grill for about 1 minute on each side.

Place sliced chicken on each pita, top with tzatziki sauce, and add any additional toppings like lettuce, tomatoes, or onions as desired.

Wrap the pita around the filling and serve immediately.