Gisela 10 is Devil's Island 1
Stacy 01 ought to be Devil's Island 2.
Then, Gisela 11 would be Devil's Island 3.
I'm not so sure if Tia 04 fits into this. Any other file sets that have the same setting?
The Devil's Island setting must be one of the very few cases where BA himself made sets with a clear connection between them, so continuation is not difficult to put together.
1. In Gisela 10, she gets kidnapped from the yacht and taken to the island.

2. In Stacy 001, Stacy and Tia are moving gear from the yacht to the island, presumably to start the rescue mission. Stacy ends up kidnapped too.

3. In Gisela 11, both women are unconscious on the altars. One of the demons takes Stacy through the portal, while the other stays with Gisela. In the end, Kira and Tia finally arrive and rescue Gisela. Tia steps into the portal.

4. In Tia 04, Lucifer is already fucking Stacy who was brought in Gisela 11. Tia takes her place, and both end up rescued by Kira once she is done tending to Gisela. She helps Stacy out, chucks the bomb at Lucifer, and escapes with Tia.
Don't forget the all girls set. That happens first before anything else. Same women, same swimsuits, same yacht.
I mentioned the "Girl on Girl" set, yes. As you say, it fits right in the same setting. As for when to put it, I guess it's personal choice. In the case of my
storyline project, I put this set at the end. It's a way of showing the girls celebrating their success, and also their corruption, since they jump straight from a dangerous situation into fucking each other, still right next to the island. It also acts as a bridge for the next part of the story and the other sets that set it up.
Finally, you also have a Miriam shared commission.

It's the same altars+portal setting, but Gisela and Stacy aren't there. You could argue this happens before everything else or afterward. In the case of my storyline, Miriam is having her own parallel plot to the other girls', and this set occurs right before Gisela and Stacy are taken to the altars.