Almost time!!!

Hey ladies. Sooo I just entered my 3rd trimester. 27 weeks. With a baby boy. So I have a couple questions. First things first. I'm nervous out the 3D ultra sound we will get Wednesday to see a little more detail as to how he looks. But my most basic question is "when can we start to buy things?" We haven't bought anything yet because we fear we may have a miscarriage or still birth. And when can we have a baby shower for our little jr?