When it comes to layering, not quite everything is going to work. My personal rule of thumb is only to layer tops that at least have a short sleeve. Strappy tops, halternecks and strapless tops look pretty cheap and tacky if worn over a fitted long sleeve top. That doesn't mean we can't make them work though. A simple solution is just to add a cardigan or jacket on top. This also solves the problem of having bra-straps visible through the long sleeve tops, which is a both a fashion and hijab faux pas.
This outfit is something I'd wear if I had uni during the day, and was going out with friends later on. Team a pretty printed satin dress with a long black cardigan and wide leg trousers. To cover up the neckline, I usually wear a black t-shirt underneath the dress, and a large coloured pashmina will keep you warm too. Satin flats are comfortable enough to be worn all day, but still look glam - look for brightly coloured or jewelled versions if you prefer. Then just add a big bright handbag to compliment one of the colours in the dress:
Green paisley border print dress £50, Debenhams; knitted long line cardigan £32, Topshop; green pashmina £6.99, The Hijab Shop; black button wide leg trousers £25; pink ruched buckle bag £25, both Dorothy Perkins; black satin rouched bow pumps £12, Debenhams.