You need a pair of boots or trainers that will allow you to walk about in below zero temoeratures and may be a foot or so of snow.( trainers need to be all leather and not fabric.)
When we were in Bansko in March you needed warm clothes to walk around outside the hotel as it was perishing. Nobody dressed up at all - jeans t shirts with jumper over the top , mind you we did not go in a club!
Was also in bansko last march - took black heeled boots to wear out but a) they weren't practical in the snow and i nearly ended up on my ar$e a numb of times and b) they weren't warm enough and nearly froze me feet off!
Girls get them moon boots out, I have bright pink ones that I think look wicked, keep my feet toastie & best of all it taught me that dancing in flat shoes is so comfy!!!