Uhhhh. Shopping block! ?

Before I knew the gender of my baby, I'd always day dream of all the stuff I wanted to buy him/her. But now that I know what I'm having (a little girl!) I have no idea what I should buy first! Or what I should buy at all! It's just like this huge block lol. What are the most important things that I should buy first? Please help. I have four months to go before she's here. Help please xoxo