Hello, Luis! In addition to traditional squats, also perform plie squats with your legs placed somewhat wider than shoulder width and your knees and toes in turnout, AND don't forget about lunges with both legs on the floor!
Also, you may want to check out some of Cathe's workouts that have rear leg extension drills as you are standing on one leg. These really help the glutes.
Above all - be patient. Muscle mass development cannot and should not be hurried. And you don't want to overdo strength and mass development in one muscle group, because that can create a muscle strength imbalance in that group's opposing muscle group, which can lead to proneness to injuries.
A-Jock