I think the key to dressing stylish for business casual is to find pants/skirts that fit you well.

Once the pants fit, then any top would do.

As to tops, an ill shaped white shirt really detracts from the whole outfit. I also find some of the "business" style blouses at Banana Republic or J Crew very matronly. So I go for nicer style blouses, such as the gorgeous shirts from Aritzia or some of the "simpler items" from Anthropologie.

Here are a few examples: here, here, and here

These two are expensive brands, so I ususally wait for 40% sales on these items.

Other chic brands to splurge on and have crappy sales: &other stories, Sezane, and All Saints. These clothes are just beautiful.

Also, sometimes, pairing a plain tshirt with the right pants/skirt, with an addition of a form fitting blazer (usually a neutral color), makes anyone stand out.