When to have a baby

When, in your opinion, is the perfect age gap between babies? Let’s say you have one (or two or three) and your planning your next baby. How big of a gap between your current youngest and your newest? All opinion based, no right or wrong or debatable response but if the poll doesn’t match up, pls leave a comment! (It’s for research for a child development class. This is the opinion portion of my essay, there’s also a research portion so you’re not “doing my homework for me” so no worries there). Does your opinion change depending on what number baby? Like first two can be two years apart but then the third is more like 4 years? Or all the same? Please & thank you!