I have to say, (I guess like many others), watching a girl getting fucked on camera for the first time turns me on a lot. Maybe even more so if it's not just a regular b/g scene, but her taking part in a group scene with experienced other talents. One of the benefits might also be that the camera is not focusing on them all the time, leaving them some space.
Sasha Grey had a big mouth and took it like a champ in Fashionistas Safada.
Correct me if I'm wrong, but afaik Dakota Skye shot her first scene in a FFFFM for BFFS. She was nervously watching the other girls, eager to grab the penis when it popped up in front of her face before she'd change her mind. And when it came to fucking, she had trouble getting it in for a while before adjusting to it and enjoying the pumping she got.
Do you know of any other debut scenes of girls (first shot) that were group sex scenes?