Wow, didn't realize I was the "spokesman" for what to wear with the Ireland's/Irish National tartan.

Greendragon,
I have a BUNCH of those Wal Mart polos. I wear them to work all the time. The orange polo I'm wearing in that bottom picture with my cousin is one of those polos.

I've also worn a black polo with that tartan. Make sure your shoes/boots belt (if you choose to wear one) and sporran are all black as well, and you'll be set.