You know, part of Matt's advice on what is already in your closet working fine brings up another related bit, that I think is often missed with some folk. What is worn with the kilt is largely dictated by what would or could be worn without the kilt at a similar event.

Outside of kilting, except when the situation demands it, I am a T-Shirt and Jeans guy. I have several T-Shirts that are funny and kilt related, yet I am just as likely to wear another T-Shirt with my kilt if the situation would be one where I can wear one without a Kilt. The decision to wear a tie, or a jacket or moving forward into formal wear, is no different with the kilt than it would be with trousers.

As for the puffy pirate shirts, I used to have two of them, they both wore out. I was going to replace one of them, as it is quite comfortable, but the particular style turned out to be quite a bit more expensive than I remember it being years ago. The cheap ones, really don't do it for me at all. However the places one can wear one of those shirts is pretty limited, at least to me.