I like wearing blouses with jeans. For me, frills and flounces can seem a bit overwhelming, so I like halter neck tops and blouses with a tie neck bow.
I have been wearing silk scarves as belts in my jeans with tucked in tops - it is a twist on wearing a belt and can be fun to co-ordinate the blouse with the scarf.
Of course heels elevate most casual outfits, but I have recently been travelling and wearing my sneakers, so scarves and bags have been the way I have looked a bit more dressy, even though I was wearing jeans and sneakers.