Nicole, a waistcoat refers to what we call a vest, I think.
I am struggling with this style myself, so I can't give much advice. What I can say though is that you should avoid jeans, lest it become like 2 of the 3 pieces needed to make a 3 piece denim suit. I think it would be best contrasted with a slick pair of trousers and either a blousy or knit top.