I like the newest one and the "old" Gaga the best. On the newest one, light is very realistic, clear, soft and really cool. And you really captured the model on this one. I see you've had some anatomy problems, like with the relation between the nose and lips, though the newest one is much better (better than most of my portraits, by the way). Maybe a bit more of 3D geometry at the sketch level will help? My other suggestion is to look up for a reference pictures with clearly defined, hard light, to see how lights and shadows are building the shape. Heavily edited magazine photos with uniform light aren't the best choice for learning. And of course, don't forget about life drawing - it's the basic on all levels.