To memory, drow have never been conservative in their dress. Every time you see pictures, it's leotards, tabards, weird dungeonpunk stuff that you'd wear in hot caves where sunburn isn't much of an issue. As the strong gender, the women are likely to wear utilitarian stuff, trousers and short skirts rather than long flowing gowns that would inhibit them in combat. Drow men, restricted, would be likelier to wear such flowing gowns by custom. Possibly form-concealing in an arabic fashion (keep them men-folk safe from the thieving eyes of jealous neighbours).
So an uncustomary drow man would likely wear trousers or bare legs under a skirt/kilt. Would he be allowed to do so? It depends on how egalitarian the drow of that region are. If they're allowing their menfolk to study the Path Of Mobile Artillery (wizardry), they're probably OK with it (you don't send purty little things off to war, do ya? If you let 'em study, you're admitting they're kinda human, um, drowian), although such people will be looked at funny. Maybe groped every so often.
If the campaign world features female adventurers, it's likely that gender relations aren't so cut-and-dried. Trouser-wearing drow men are going to be rare, maybe feature on the covers of raunchy magazines (if they had such things), but they'll be there. And they'll look weird and pretty.
