Should you learn a particular dialect of Irish and stick to it? Many learners make a point of doing so, but I have certain reservations about it. To start with, for some marginal dialects there is very little material available, and all there is is contaminated with unacceptable anglicisms typical of what we call terminal speakers (a terminal speaker, “cainteoir foirceanta” in Irish, is a native speaker who does not speak the language on a regular basis and isn’t sure about the correct language anymore). Thus, dialect enthusiasts run the risk of incorporating what is definitely “bad Irish”. Moreover, there is what I call petty dialect enthusiasm. Petty dialect enthusiasm means that you make a big fuss about using the words and inflectional forms of a particular dialect, while using heavily English-influenced syntax (again, for those not familiar with the slang of my trade, the term”syntax” means “how words depend on each other in a sentence”).
It is my impression that syntax is the key to the difference between “that dreadful school Irish” and that mythologically perfect Gaeltacht Irish which you can only learn sitting at the feet of some distinguished Gamaliel in a druidic-bardic hedge school. The reason why “standard Irish” is so disliked is the fact that it is all too often paired with poor syntax and heavy English influence. The reason why new terms are disliked is the fact that you only meet them in the context of poor syntax and heavy English influence. Myself, I have spoken with Gaeltacht people in an Irish that is very near to standard Irish, with a pronunciation based essentially on the standard one introduced in Focloir Poca and Focloir Scoile. They were quite happy with the kind of Irish I spoke to them, and said that it sounded like Gaeltacht Irish, but not of any particular Gaeltacht.
Thus, it is possible to use standard Irish in a way that is acceptable to the native speakers. And I am afraid it is possible to use faux-dialectal Irish in a way that is as hair-raising as the worst standard Irish. However, focusing on one dialect is not a bad idea – although not as an end in itself, but rather as a way to good Irish in a more inclusive sense. I became known as an enthusiast of Ulster Irish, but before that I studied Connemara and Blasket Irish quite extensively, and this is precisely why I got so fanatical about Ulster: it was a new kind of Irish,which really had a taste and feel of its own. By starting with one dialect and learning it thoroughly, you can develop an appreciation of all dialects, and enrich your Irish by picking up new words and expressions as you go.