I started mine around 7 weeks. I didn't see any reason to wait to think about what I'd like to get. I haven't bought much yet, just some cloth diapers since if we buy a handful of them every month we'll have enough when Baby arrives. I picked up a stuffed animal last week as well. That's it for buying stuff.. but yeah, I started the registry early.
Of course, the registry is still a work in progress. We find out gender when our Panorama results come in next week, so I think DH and I will finish the registry once we know if it's a boy or a girl. (My gut says boy and as of my 11w scan, the ultrasound tech is inclined to agree!)
PS: A huge congrats on your pregnancy. I've gone through the whole IF/IVF/mc/ectopic thing myself.