Hi and help please.

I haven't really ever had a decent space to plant in before this summer - yard renos... now I do and I'm dazed and confused over what I can do in it. I would like to plant an area with cosmos but don't think that I will have a nice full display if I follow the planting spacing listed on the little tag that goes with the cell pack of plants. Can they be planted closer or am I just impatient - in my zone they are not exactly going to become bushes overnight - although my tiny yard does become an oven during the day. Your advice would be appreciated

Fern