In a bowl, whisk together olive oil, minced garlic, lemon juice, oregano, cumin, paprika, salt, and pepper. Add chicken, ensuring it's evenly coated. Cover and refrigerate for at least 1 hour (or overnight for best flavor).

Heat a grill or skillet over medium-high heat. Grill the marinated chicken for about 6-7 minutes on each side, or until fully cooked and the juices run clear. Let it rest for 5 minutes, then slice thinly.

In a separate bowl, mix Greek yogurt, crumbled feta, grated cucumber, minced garlic, dill, mint, lemon juice, salt, and pepper. Stir until smooth and creamy. Chill in the fridge while preparing the chicken.

Place pitas on the grill for about 1 minute on each side until warm and pliable.

On each warm pita, layer the sliced chicken, creamy tzatziki, and a variety of fresh veggies like sliced red onion, tomatoes, cucumber, and lettuce. Roll tightly and serve immediately.