where wouldd this fit ibto your skincare routine, ie before or after vitamin c or retinol or ???

This serum has bakuchiol which is a naturally derived retinol alternative. It’s more gentle. But I don’t think you would need retinol with this serum. Not sure if it has any actives that would interfere with vitamin C but I would say start out by using Vitamin C in the morning and this as your active at night.