Drizzle olive oil into a 12 - 15-inch skillet over medium heat. Add shredded beef, onion and garlic. Cook until onion begins to become translucent. Remove from heat and spoon half of beef mixture into a medium bowl.
Add the following in loose layers, making sure that bites of all ingredients can be made by lifting a chip and scooping: tortilla chips, shredded beef, beans, cheeses, pico de gallo. Repeat layers until skillet is full and mounded, reserving about 1/2 of the pico de gallo for serving alongside nachos.
Place in oven and bake until cheese is fully melted. Remove from oven and serve warm with sour cream, guacamole, and additional pico de gallo.