The earliest Baptismal record is, as you probably know is Ballaugh 1607 though most parishes are nearly a century later (full list at www.manxnotebook.com/famhist/genealgy/church.htm) - the Manorial rolls will go back to 1511/1515 but they do not give detailed genealogical info - some sequence can often be inferred by the change of tennant (and the reasons for this in the Lib Vast) + eg rental on Intack may give some women's names but dates can be very tenuous in that changes might not be recorded for some years after the event.
There are a few very early (late 16th C) wills (eg those published in 2002 Fam Hist Soc journal) but their preservation seems to have been accidental though there may be more to be found.
Pre 1500 Manx records are few and far between - probably most perished in the sacking of Latham in the Civil war and the burning of the Milntown Christian muniments in the early 19th C.