There are LOTS of wrong ways to wear a kilt! (1) Wearing any undergarment that *shows* is one (in the Highland regiments you are out of uniform if you wear *anything* under the kilt - unless participating in athletics, dancing, or marching band, because all those activities are likely to make your kilt flip up. But if you DO feel the need to wear something, nobody should know. I have seen men with their boxer shorts playing peekaboo under the hem.) (2) Wearing a kilt that is too long (should hit between the center and top of the kneecap). You'll occasionally see one too short, usually the re-enactment folks who are wearing belted plaids, but that's a whole nother story. (3) Wearing a ladies' dress thinking it's a kilt - the pleating and heavy weight of a kilt is distinctive (utility kilts fall in this category. They are not pleated correctly and the fabric is much too lightweight). (4) Wearing inappropriate accessories. If you go casual, a plain leather sporran, a nice belt, wool hose and sturdy shoes are about it.
Some people gripe about the tartans; I don't. Only 3 or 4 "setts" (patterns) predate the 1746 outlawing of tartan and Highland dress. Most were created in the Victorian era, after Walter Scott made the Highlands fashionable.
Since I’m not in a Highland regiment, I don’t feel the compunction to go “regimental” much.
I have a canvas utility kilt, and it’s plenty heavy! I use it mainly for yard work and other house chores. No-one knows what’s underneath it, and if they ask, my stock answer is “shoes and socks.”