Carla, I hope you’re feeling better today!
When I found FTD, I was already eating pretty close to the GAPS intro. I haven’t been able to reintroduce anything successfully, but it’s quite possible to follow a hybrid of GAPS and FTD. It’s not any more difficult than GAPS alone, if you were already mentally prepared for that. And as far as I can tell the combination will give faster results for severe digestive problems.
On any of these diets, you do need to experiment and figure out what works for you, because all our bodies are different. GAPS has a lot of advice that’s helped me, but also includes a number of recommendations I can’t tolerate. I doubt FTD alone would work for me either.
Some people need to make changes gradually or they get overwhelmed. Others prefer a drastic change, start out very limited and get a baseline as soon as possible so they can start testing foods. After experimenting nonstop for a year and a half, I wish I had been much more restricted from the beginning — but I don’t know if I could have coped with a more sudden change at that point.
Whatever you start with, I hope you see improvement soon!