I have just had DS2. DS1 has just turned 2 years old.

I found that all I needed were new bottles and some clothes (we have moved and the temperature is warmer here).

I had moved DS1 into a bed so we could re-use the cot so I suppose the bed was something we had to buy.

DS1 is walking quite well so I didn't get a 2-seater pram. We did get another stroller so if we do go out for long distances, DH and I both have a pram but I don't think we need a 2-seater for everyday use. You can always get a skate that sits on the back of your current pram for the older child to stand on instead of a new pram.

That was all I did and so far it has worked very well.