Here are some New Years' greetings and expressions in Irish (Gaeilge), with a few in Scottish Gaelic (Gàidhlig) thrown in at the end (for more Scottish Gaelic information, see that part of the forum). The text in brackets below is either optional or involves a choice (in the latter case, the choice is indicated in the translation).

Athbhliain / an Bhliain Úr
New Year

Oíche Chinn Bhliana
New Year’s Eve

Athbhliain faoi [shéan 's faoi] mhaise [dhuit / dhaoibh]
Happy [and Prosperous] New Year [to you/you all]

response:
Go mbá hé [dhuit/dhaoibh].
The same [to you/you all].

Let's go outside to listen to the New Year bells.
Gabhaimis amach chun éisteacht le cloiginí na h-athbhliana.

May we be alive at this time next year.
Go mbeire muid beo ar an am seo arís.

and, to throw in the Scottish Gaelic versions for good measure:

Bliadhna Mhath Ùr
Happy New year

Le gach deagh dhùrachd airson a Bhliadhna Ùir
With best wishes for the New Year

Oidche Challainn
New Year's Eve

Callainn / Latha na Bliadhna Ùire
New Year's Day

_________________
I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.

Time to bump this up and sticky it for the season.

This thread is locked, because it was getting spammed.
If you have additional greetings to add, start a separate thread and one of the moderators can merge them in if they fit the theme.

_________________
I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.