Welcome to the board.
I agree with you, the Irish national tartan is just beautiful.
Topside , dude just wear what you want within reason, try wearing what you normally would and look at yourself in the mirror.
Ask the wife if you look ok, woman usually know what looks right and what doesn't.
Do yourself a favour and don't put too many rules on yourself with I can't wear this or that or you'll never do it.
Best wishes.