In a medium bowl, combine the chili powder, cumin, oregano, garlic powder, onion powder, salt, pepper and olive oil. Add in the shrimp and toss until completely coated.
In a second bowl combine all the guacamole ingredients and mash together. In third bowl mix together all the ingredients from the pico de gallo.
Heat a pan over a medium heat. Add shrimp and cook for a couple of minutes on each side until shrimp are no longer opaque.
To serve, divide the guacamole evenly between the tostadas, top with shrimp and the pico de gallo.