What do you think is the ideal age to have your first child?

Whenever you are financially stable hun.

I agree with @Bone Alone. I believe 30 is quite ideal. Though, it's still completely possible to have a child sooner and still be a happy family. It's just, at 30, you're more likely to have a good education/stabled job, a mature mind where the wild days are over, and perhaps have a decent amount of funds in savings just to be financially secured with your child. Maybe give the child a childhood they won't forget (like to Disney World!) or a jump start on their college funds (and if they don't decide to go, use it to help them with their first car or house or wedding or something). 

There is no ideal age to have the first child.

My opinion? Doctors say early 20s to mid 30s

As long it's any age over 18.

i think it depends more on how mature they are than how old they are

At least 30. From rats, young mothers are bad mothers. She has no idea how to take care of them. Old mothers are makes faulty rats because she has old dna. So you want a rat that’s a full adult but not middle aged. 

Same applies to humans. A female that’s not a teenager and not middle age makes the best kids because she’s mature enough to know how to care for the kid but her eggs aren’t so old that it produces messed up kids.