First thing, start squatting and deadlifting, both exercises will in theory hammer your glutes, although this doesn't necessarily hold true. Some people just build up their legs from squatting with little glute hypertrophy, and deadlifts just aren't for everybody. I think a solid foundation of wide stance squats and deadlifts would be a good start, and then add in some glute isolation movements like glute bridges, barbell hip thrusts and back extensions as well as some lunge-pattern movements like walking lunges and step-ups. Put these together into one or two lower body workouts per week and you'll be doing a lot to improving your glute composition.