For me personally, if I had nothing at all, this is what I'd start with (I was thinking about this quite recently).
Black jeans, blue jeans, cream jeans (one of each)
1 pair wide black smarter looking trousers
A straight, knee-length or slightly shorter, black skirt that looks good with or without tights
maybe a lightish blue denim skirt, but that would be a lower priority
3 or 4 fitted, scoop-necked black 3/4 length sleeved t-shirts
1 blue and white stripy t-shirt
1 plain white or cream shirt
2 cotton jersey dresses, maybe one black and one a classic pattern such as polka dots, chosen to look good dressed up or down
1 longish black cardigan (preferably cotton)
1 black v-neck jumper (preferably cotton)
1 loose black cowl-neck jumper in a soft warm fabric (cashmere would be great but realistically probably wool-mix)
1 or 2 slubby cotton jumpers in light neutral colours such as taupe, dove grey or oatmeal
1 black jacket that would look like a suit with either the wide trousers or the skirt
1 leather jacket, either black or a light neutral
1 warm winter coat - maybe a classic belted wool one in either black or grey
Ultimately, when expanding this basic wardrobe, a light coloured trench for spring
short, casual/chunky tan or taupe boots
short, more elegant/streamlined black boots (but I'd probably get long ones too, in the end)
lowish heeled smart black shoes (maybe ballet pumps or pointy flats)
medium-heeled classic black courts
white low-top Converse
Underwear/socks/tights to work with all of the above
2 swimming costumes
Trainers suitable for running, sports bra, sports socks, 2 pairs leggings, hoodie, couple of loose comfortable t-shirts suitable for running and/or yoga
hat/scarf/gloves in 2 different colours, either black or cream and then a bright fun colour