I’d say learn whatever you have resources, just be aware which dialect it is. If you want to communicate in Irish, read press in Irish, etc., you’ll encounter all the dialects, and sometimes possibly even Manx and Scottish Gaelic too, so it’s important to at least be familiar with them enough to have passive understanding.
If you want to focus on a single dialect, do it in your writing – if you do exercises to a textbook, or if you write in Irish on the web, or if you write an Irish-language diary, try to use that dialect’s forms and idioms, but still learn to read and understand the other ones.
And Munster dialect with its all synthetic verb forms, consistently pronounced consonant in -aidh, -aigh, and /mn/, /kn/, etc. instead of the rest-of-the-Gaeldom /mr/, /kr/, etc. is cool.
TLDR: IMO learn from whatever good sources you have, and learn it all, just be aware of the dialect of the particular source.