This depends on one's aesthetic. I wear precisely the same shirts, waistcoats, and shoes when I'm wearing a skirt as when I'm wearing trousers. Now, I can get away with that because most of my clothes are geared towards a reasonably professional look, and I'm after pretty much the same look when I'm wearing a skirt. So, in my case, it is quite literally just swapping out the trousers for the skirt and making sure everything else "goes".Men who wear skirts generally need to have two sets of clothes - one set to go with their trousers when they wear them and one set to go with their skirts when they wear them.
The only difference would be legwear, and even then, only occasionally. For the most part, I've retired the older style of socks I used to wear (mid-to-lower calf-length black and navy ones that looked positively awful under a skirt) in favour of more skirt-friendly styles. If it's cold, I'll wear opaque tights for warmth even under trousers (although I won't wear sheers that way), and I've found that knee-high hosiery works just fine for either longer skirts or trousers.
The way I do it may not work for you (a hypothetical "you", not a specific you! ); your aesthetic is quite likely different from mine, and you'll need to pick your way along your own path. Whatever that path is, do enjoy it a long the way.