First thing to watch, Scooter:
In English, Irish Gaelic is formally called "Irish" and only Scottish Gaelic is formally called "Gaelic". (I blame the Brits and their divide and conquer policy for that one but that's a whole 'nother forum ...)
So, if you want to learn Irish don't buy any texts that say "(Teach Yourself/Learn, etc.) Gaelic" because they will be about Scottish Gaelic, not Irish. (Just letting you know so as you don't waste money unnecessarily.)
"Learning Irish" is great for grammar AND it is one of the few texts with real native (i.e., Gaeltacht) speakers doing all of the readings (the fact that it is in my favourite dialect is irrelevant and if you believe that you'll believe anything.

) (@others - if there are other more recent textbooks that have real native-speaker soundfiles, please let me know.)
BUT you'll notice a real love-hate reaction from all quarters regarding "Learning Irish". "It doesn't teach conversation", "it's methodology is outdated", "it's too hard to get through", etc., etc., all of which are no doubt true but the fact is it has no real rival (except maybe the really, really expensive linguaphone courses?) and has stood the test of time.
My suggestion is to use "Learning Irish" as your core grammar base (as long as you don't mind learning Connemara Irish) and then dabble with whatever other courses you hear of for conversation.
I myself used Buntús Cainte for conversation practice.
If you get stuck with Learning Irish, you can always post your questions here.