Best wishes for Christmas and the new year
It should be: 'Le gach dea-ghuí i gcomhair na Nollag is na h-Athbhliana' It means: 'With every good wish for Christmas and the New Year'.
I think you mean Le gach dea-ghuí inniu agus i gconaí.
Translated from Irish Gaelic it means:
Best wishes today and always.
"Slaindte" should be "Sláinte" "beannuchtai" should be "beannachtaí" "deoine go le ar" should be "gach duine" "Sláinte agus beannachtaí ar gach duine anso" means "Health and blessings to everyone here"
"Nollaig shona agus athbhliain faoi mhaise daoibh" means "Merry Christmas and a happy New Year"
le gach dea-ghuí / le gach dea-mhéin / le dea-ghuí / le dea-mhéin
Scottish Gaelic: le gach deagh dhùrachd.
If you mean the standard letter-closing expression (and not 'please send my best regards to...') as far as I know, it should be 'Is mise le meas' - the same as 'Yours sincerely' or '.... truly'
Tá an crá na croise le gach duine
Irish
Le mo ghrasa mise, agus liomsa mo ghra
Bíonn cúis le gach ní a tharlaíonn
I believe it should be "Tá tú an-dathúil agus ceapaim go bhfuilim i ngrá le do phictiúr." "You are very comely and I think that I am in love with your picture."
"Best" in Gaelic Irish would be translated to "is fearr".
In Irish it's "is le creideamh a shiúlaimid agus ní le radharc na súl é"