Now, I think FE9/10 came first, as Vincent describes here:
As we can see, the Laguz do not need their stones, which brings us to FE6/7. In FE6, it describes the Never-ending Winter and the need for the Manaketes to imprison their power into their dragonstones. If this is the reason that the dragons need to contain their power, it puts FE1/2/3/13 after them, as Manaketes use stones in those games. The Dragons do not seem to need stones in FE4/5, so they are before FE7/6.
At this point, we just have FE8. Where does it fit in? I think it might be last, but it could be between FE3/13. Manaketes do need stones in this game too, and so it would have to be after FE7/6.