Is there a Gaelic equivalent for the saying "The journey of a thousand miles begins with a single step" ? I'm assuming a direct translation doesn't have the same meaning

I know nothing is always right. Thoughts of people, the truth will come true.

I can't think of anything really close, in the sense of starting a journey, but there is this traditional expression:
Tús maith leath na hoibre.
A good start is half the work.
Dialectical variant (Munster, I think): Tosach maith leath na hoibre.

On a totally tangential note, there's also this expression, which I love both for the play on words at the beginning and the sentiment:
An timpeall chun an teimpeall is an cóngar chun an bía.
[Take] the long way to church and the short cut to food.

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

As idioms go, "Tús maith leath na hoibre" is pretty good I think. You'll never get one exactly the meaning-wise, but the sentiment is pretty damn close here IMO.

Would this work ? -

Tá ar dtús gach turais fada an chéad choiscéim ann.

To do a big ,long-lasting task "Rome wasn't built in a day"
the Irish idiom is "De réir a chéile a thógtar an caisleán" literally "stone by stone a castle is built"

"The journey of a thousand miles begins with a single step" is a straight translation from the original Chinese apparently, so I don't see why we can't do the same in Irish.

Tosaíonn aistear míle míle le coischéim amháin ("Thousand" and "mile" are the same word in Irish.)


('There is at the beginning of every long journey a/the first step')

Not quite. 'Ar dtús' is a kind of adverbial phrase and can be translated as 'at/in the beginning' in the sense of ''(at) first", so it can't be used here. > 'i dtús/ag tús gach turais, which I'd put at the beginning or end of the sentence because I think the subject 'an chéad choischéim' is too far removed from its verb. Maybe 'bíonn' instead of 'tá'?