A challenge that comes with a rapidly growing body is what type of clothes to wear, and which items to get as maternity. I've avoided getting mostly maternity clothes (especially shirts and dresses) based on the idea that I'd like to be able to still wear these pieces after my pregnancy. A way to accomplish this is through flowy tops, stretchy jersey fabrics, button ups and cardigan sweaters. They can all be mixed and matched throughout your pregnancy as well as after baby.
I bought two button up shirts from my local J.Crew outlet in one size larger when I first started to show. They helped during that awkward in between phase before you have an established bump and look like you just ate an entire pizza. These pictures were taken when I was 18 weeks, and the shirt still buttoned up easily. As you grow, you can continue to where these shirts until you can't button them anymore, and even better, these can be used after.
My maternity faux leather leggings from Asos are a new favorite, and I've already worn them many times. I made sure to buy them a size larger than I needed initially so that I could continue to wear them as long as possible. Leggings are so comfortable during a very uncomfortable time, and since I wear them so frequently, having a few pairs in maternity is totally worth it. This particular pair is also a bit more dressed up than your typical cotton variety.