You are going to need #0 double points!

The romper uses sock yarn & I used scarps so do not know how much but only little, as is usual for these little girls. A dress can be made with 30 yards and I think it will take a little less. I am estimating about 15 yards for the hat.

I knitted the hat in the Loops & Threads and also in the Knit Picks lace and both fit, the lace being a little smaller but not significantly.