First of all, what a wonderful site. Thank you so much for any help you can spare towards my request.
To give some context, I want to tattoo short concise mottos do draw inspiration from. I tend to not do the hard work when it really matters in my life and i want to help remember why its important in this tattoo, because others depend on me and I need to change. So that's where "do work" comes from. I'd be open to other phrases if better or easier. "work hard" or even if there is an Irish phrase that embodies this sentiment similarly as "nose to the grind stone" for example.

Second, I've been guilty of placing myself and my own selfishness before others I care about. I'm working on change and want to have a reminder to help me make better and more selfless decisions. That's where the "others before yourself" comes from.
Same as above, If there is a easier, or better way to convey the same message. I am open to your advice.

Since this is a tattoo, old spelling and characters would be desirable visually, but not a must have request.

Thanks again

It is really surprising I have not seen this issue for a long time.

Literally, your first requested phrase could be Déan d'obair ("Do your work"), but that comes across as more of a command than a wise saying. For the second phrase, you could use Obair go crua ("Work hard"), but again that sounds like a command. There are a number of variations on this second one, using alternate words for hard, diligent, etc.

I'm not aware of an established Irish equivalent for the "grindstone" phrase. I found this in the dictionary as a purported equivalent (in a form which I've adjusted to fit your goal), but it doesn't seem to me to be a true equivalent:
Coinnigh do dhá cheann i dtalamh agat
Keep your two feet on the ground.

There is one traditional phrase which might suit your purpose:
Is fearr obair ná caint.
Work is better than talk.

Less directly on point, but also about work and/or cooperation in work, you could try one of these:

Tús maith leath na hoibre.
A good start is half the work.

San obair a fhaightear an fhoghlaim.
It’s in the work the learning is obtained.

Múineann an obair féin duine.
The work itself teaches a person.

I ndiaidh a chéile a thógtar na caisleáin.
Many hands make short work. [more literally: "Together with one another the castle is raised."]

Ar scáth a chéile a mhaireas na daoine.
People live in one another’s shadow. [i.e. they depend on one another]

An rud a scríobhann an púca léadh sé féin é.
You should take responsibility for what you do. [more literally: "What the púca writes, he should read himself"]

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

Err, I think that's what you want... Your version meant something a little different

I don't think this is the correct meaning of i ndiaidh a chéile but successively, one after the other.
Dá dtóigfeá an caisleán "i ndiaidh a chéile" ... you arrange its parts in the correct sequence, stone by stone, not "together" in the sense of collaborating with others.

It isn't "short work", in fact it is used to say the opposite: Rome Wasn't Built in a Day.

I see your point, and have corrected it. I copied it out of a list of proverbs given out at a course I took, and didn't look carefully at it.

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

That also makes sense. I copied it out of the same list as mentioned above, and did actually wonder about the interpretation of this one, but since the teacher was a native speaker I didn't think to question his interpretation.

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

BAHAHAHAHHAHA
bhain an ceann sin gáire maith asam!!

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ЯГОН ТОҶИК НЕСТ ИНҶО???

That would be my interpretation too. One after the other/gradually.