OH! To answer your question, since you had the baby in May I'd wait until at least January-May. That way the baby is closer to getting out of diapers when you have the next one.
I consider close in age about two years apart. My husband and I started trying for number two when our son was eight months old and didn't get pregnant until he was 20 months old. I'm now 28 weeks pregnant, due Dec 9 and Elijah will be 29 months old when I have her. If we decide to go for a third soon again, I'm gonna want to start when this baby is about 8-12 months old.