All our gymnasts have grips straight away, regardless of their level, so they learn it with grips right from the beginning - A couple of coaches allow their gymnasts to 'have a go' without grips and they get their kip straight away, but then it is a nightmare getting them to put their grips back on!
I've been teaching my girls kips since January - one got hers last month, the other one is really close and just needs to get the grip shift on her own now!