I waited till 24weeks.. I brought stuff here and there before that but no big stuff.. 24weeks is when they have a chance of survival outside the womb. 26weeks is better. It really depends on your situation.
I do have things from my first baby but we're only starting to buy things next month when I'm about 25 weeks just to be safe. I'm a little scared still but all our appointments have gone really well and I got given a fetal Doppler to ease my mind.
They didn’t necessarily consider me high risk after loosing my first baby but after loosing her at 22 weeks and being pregnant again I won’t be doing any buying/planning or preparing until I hit about 30 weeks or so. That’s just me. I went so crazy on my daughter and lost her I financially can’t do that again and not bring home a baby.