All my kids are around 3 years apart. I wanted that for some reason, more so it was easier on me. I wanted the first sleeping well & in their own bed & out of nappies before I had the next. Sometimes I wish I had them closer, but i'm happy. They fight like you wouldn't believe sometimes, but are best friends other times. Same as all siblings I guess.
I don't think there is a right age gap. whenever your ready.