1. In a small bowl, mix together the chili powder, cumin, salt, and pepper. Rub this spice mixture over the chicken strips.
2. Heat olive oil in a skillet over medium-high heat. Add the seasoned chicken strips and cook for 5-6 minutes, or until cooked through and browned on all sides. Remove from heat and set aside.
3. Warm the tortillas according to package instructions.
4. Assemble the tacos: place a few slices of avocado on each tortilla, followed by some shredded lettuce, diced tomatoes, red onion, cilantro, and cooked chicken strips.
5. Serve immediately with lime wedges on the side for squeezing over the tacos.
6. Optionally, serve with sour cream, salsa, or shredded cheese on top.