hi there!
I didnt use any blankets or sheet in the cot for the first 6 months - we wrapped bub in muslin wrap and another blanket if cold. I had about 6 and this was enough to rotate.

My little ones both went in to sleeping bags early and this prevented them getting trapped under sheets as i found they will crawl close to snuggle in them.

As for growsuits. I had about 6-10 and about 15 singlets.

I dont know when your baby is due but i found size 000 in the best as although a little big to start they grow into them very very quickly.

I have 3 cots sets which i rotate and use now. i never run out.

You will have time after the baby is born to buy more so dont worry xx