When do you start buying stroller and carrier?

Once the pregnancy is stable and I have exhausted my freebies and collected the hand me downs, I collated what I have and then bought everything except baby carrier and backup milk powder during sales. I was still 4 months from delivering when I whacked the 11.11 sales. Cost saving is still most important. I didn't buy carrier yet because some of my friends found it a complete waste as the baby didn't like/started walking too early/didn't fit their lifestyle. I bought just 1 week worth of infant clothes and infant diapers too as I don't know how big the baby may be.