As has been suggested already, I'll just parrot some good advice.

If you want to wear a kilt more "appropriate" for an Irishman, you can check out a saffron kilt, an Irish county tartan (which can be quite good looking), or one of the many Irish universal tartans (national, pride, heritage, etc).

Or, if you find a clan tartan that you really like, wear it. Double-check that there isn't a restriction on its use here: Scottish Tartan Registry

Or, if you like, you can always wear any of the "universal" tartans: Black Watch, X-Marks, Scottish National, etc.

Like has been said, if you wear a tartan, know something about it, people will ask.

And the most important rule: wear a kilt!