I would suggest starting along the lines of-
two pairs of jeans - one dark and slim leg cut for heels and one dark and slim leg cut for Converse-type things;
one denim skirt - either just above or just below the knee in a shape that suits you - the Hobbs sale had some cute slightly kick-pleated ones iirc, or you could get a denim pencil skirt or a classic just above the knee straight one (Gap or M&S usually good for these);
a cashmere or cashmere mix v neck jumper in grey or black (if these suit you) or another colour (if they don't) that can be worn with denim, or with other bottoms;
a black long sleeved t-shirt, a white one and a grey one with a neckline to suit you (eg for me, this would be scoop-neck);
a pair of brown knee high boots; a pair of coloured ballet shoes and a pair of grey or pewter leather Converse-alikes;
a soft day dress, just above the knee - either knitted if norks allow, or perhaps a cotton/viscose mix if they don't;
a blazer - grey often works better than black as it goes with more colours;
a top to dress up the jeans for evenings.