With my first pregnancy, I started wearing a belly belt with my usual pants/jeans around 12 weeks. I move to maternity pants around 15 weeks. I only bought a couple of maternity tops because I found things in my wardrobe that worked with my belly.
With this second pregnancy, my belly popped earlier & I didn't bother with a belly belt, I just started wearing my maternity jeans/pants around 7 weeks. They are so comfy!! Once again, I'm not bothering with maternity tops but I have bought a couple of dresses for summer (DD was a winter baby so I don't have any summer maternity dresses/pants).