I would hug Gaga so strong. I don't think I can gift her anything but my love. And Christina...it's kinda difficult. I think I'd give her something fanmade, something beautiful she could show to her kid and make him proud of her mom.
I would gift Madonna her masterpiece, the Ray of Light album, so she can stop making this High School Musical music is Give Me All Your Love.
I'd give Gaga a copy of Malice Mizer's Merveilles box set - concert DVD being the highlight - so she gets "inspired" and I can live through that since I was only 3 when the original concert happened. I'd also give her a day off, somehow.
I'd give Ke$ha the best makeup kit I could find at ULTA...sincerely, of course