Nothing is particularly hard, but most of it is somewhat elaborate. First of all it's important to find a pose that looks convincing enough and not too silly.
The problem with limbs is that they all should be the same size/lengths :D You don't think much about it when doing illustrations, but it's important here and sometimes it's a bit of problem. The most hard item to draw is a mantle, it's a complicated piece of clothing and adding all the variations of sleeves doesn't make it any easier.
Pleated skirts are somewhat problematic, especially since I am doing all the tartan patterns by hand, but I kinda actually enjoy drawing them! Drawing the tartan is a bit of a meditative process.