Booty building

I would follow a proper progressive program. Bret Contreras is a great glute resource. He has many programs like Strong Curves which focuses on the glutes and include key moves like hip thrusts, glute bridges, deadlifts, squats and other accessories like hip abductions, kickbacks, reverse hypers etc.
There are others too. Thinner Leaner Stronger is another pretty good program with a good amount of glute work.

Also make sure you are fueling yourself. Glutes, like any muscle grow with extra calories, so eating at maintenance or above (to gain) you will see more changes vs if you are losing weight.

And make sure you get enough protein. 0.8-1g per lb goalweight/lean body mass