I did a little experiment for you and under the search term "business casual girls" on google I found hundreds of casual yet elegant looking outfits :D It's too many pics to share so I just took my 2 favourite ones. Try to do the search, you'll see plenty of good ideas :D
Pairs of grey/black/cream chinos. Knee length pencil skirts, black and grey. Tights. Oxford shirts in blues/white/pink. At least one blazer grey or navy. Low, Cuban or medium heeled pumps/smart work flats.
Gives you quite a few options to mix up every day.
When it comes to Business, dress pants and pencil skirts are your go to things to wear for the bottom. As for tops you can play around with several things especially if it's for casual work. It doesn't always have to be a buttoned shirt and a blazer. If the weather is warm, I don't recommend a t shirt, wear a blouse instead. I also wouldn't recommend a jean jacket. You want to keep it professional. Jean fabric and t shirts aren't professional. scontent-fra3-1.xx.fbcdn.net/.../...80918845_n.png Or a tank top like this one scontent-fra3-1.xx.fbcdn.net/.../...64470061_n.jpg Neutral colors are the preferred colors for Working Girl outfits, but it's okay to wear a non neutral color as long as it's subtle. A good example is dark colors like kaki green. scontent-fra3-1.xx.fbcdn.net/.../...15883203_n.jpg There other options for tops. A turtle neck shirt and a comfortable coat are by far my favorite. scontent-fra3-1.xx.fbcdn.net/.../...87621571_n.jpg A nice shirt like this is excellent for work too scontent-fra3-1.xx.fbcdn.net/.../...99034811_n.jpg To keep it a little more casual maybe you could go for clothes with cotton fabric and don't necessarily wear big high heels. There are various flats you could wear. Espadrilles and moccasins are good choices.
This is what I wear Shoes-Heels, boots, and loafers Skirts-Knee length pencil skirt or leather skirt. Sometimes a shorter skirt. Pants-Black dress pants, a nice pair of jeans, and sometimes leather pants Shirt/Jacket-A blouse with a blazer or a leather jacket
s-media-cache-ak0.pinimg.com/.../...a6c80fe91d.jpg Just wear a nice pencil skirt with a nice tight shirt or blouse, just make sure it's tight, and it's ok to show a little skin babe just not too much. Just play around with styles and see what fits your style best
A nice-looking chiffon blouse, pretty pencil skirt & blazer would be just about right :-) desk jobs can be boring, so you can pick the above in nice bright colours to bring some colour into the office!