Personally, I wouldn't buy anything at all - I hate buying things even when I am pregnant - just in case!!!!!
I know my sister brought heaps and heaps and heaps of boxes of breast pads before the birth of her third child, who was unfortunately a stillborn. I know that it hurt her greatly to come home and see all those, without a baby. Thats probably why I am hesitant to buy anything!!
Having said that, we have a friend who brought absolutely EVERYTHING - furniture, rockers, clothes, EVERYTHING.. and wasn't yet pregnant. I think it took her about 6 months pregnant and I think her beautiful little girl is now 9 months old....
Each to their own - if you want to buy, buy away!!!!
Good luck with your TTC journey. I hope its a short one for you.