Vixen,
I also play guitar, whistle, & bodhran & Celtic Harp & a bunch of other stuff the average mid-westrn USA "Traditional" Musician plays.    Sounds like you are intersted in Irish (Celtic) Music & possibly other traditional Music. Jigs, reels, hornpipe, etc, should be played no faster than you can dance them!! Folks often do not realize that these tunes are usually dance tunes. Until you have attended--& preferrably danced at & then played for some dances, it is difficult to understand the Music. Many Amricans around these parts make all Irish tunes sound like bluegrass. Some Jigs are slow jigs, some faster, a "pop jig" for the little ones would often be played slower than a jig for zestful adults. Jigs are often played at the tempo of reels, & no one can dance to them. Of course, sometimes musicians get together for a session/jam & go crazy with the tempo--or they are performing in a concert type setting & then the musicians play some of the reels faster than one can even comprehend the tune.
   Then sometimes an air is way too fast, reels are so syncopated & slowed that they become hornpipes. ARRGGHHH!!! An average "Contra dance" in many parts of North America has most reels at or just under 120 beats per min. The members of my band didn't really understand what I was trying to get across to them (even though I was raised around Irish Music & played in Ceoli bands since I was a teen) about tempos & such until we invited a local Irish dance instructor (originally from across the pond--Ireland) & her students to come dance while we played. I asked her to give us the tempo before each dance. My bandmates really got it after that.
   SO------I reccomend that you get you get some good recordings of good Musicians of the kind of Music you are learning. Stick to Musicians who play in the traditional style (acoustic) with no synths or rythym tracks, elec funkfuzz guitars etc. For Irish, you could start with the Chieftains, & Cherish the Ladies of course. There are lots more. Perhaps you could try your local public library as they usually have a nice selection of "folk" &/or "traditional" recordings. There is a video out of The Chieftains playing in various pubs about Ireland with local Musicians & dancers joining in which is a good representation--"Water From The Well." & also one of the Chieftains with James Galway.    There are also many local organizations which have Musicians playing/jamming with their kind of folk or traditional Music.    You should be able to get a much better understanding of style, tempo etc. if you can find some of the above
& really get into the tunes or songs.    Have fun, & good luck!