It's nice to start with a rug. That way you have a base to pull colors from. Window or furniture doesn't matter, generally it's easier to begin with the fabric with the most colors.

It's never simple exactly, but a snowball effect happens when you start with one decision. If you choose one thing, then you will be on your way! Each decision narrows down the options for the next decision!

I would purchase the furniture first because there are so many factors to go into its selection and it is the most expensive purchase. You usually will be able to find window treatments later. With window treatments, you can now even purchase them online or buy fabric to blend with the furniture. When choosing furniture, what you choose depends on lifestyle issues such as whether you have children or pets - this will even determine the color and fabric since they need darker colors and durability. I purchased a white couch sometime ago and even reading the newspaper is a nono b/c it picks up the ink.

Furniture first, then curtains and rug, then accessories like lamps, cushions...etc.

This question can have many answers like (What came first the egg or the chicken ?)
I'd suggest go for the Drapes Asap , since you have moved in , rest of the things can Follow ! :)

I suggest you close your eyes and think how you envision the room. Usually the first thing that people notice in your room are the biggest pieces of furniture. So I would choose that first. Then I would choose a rug and then the window treatments. But all these choices should be based on the vision you have in your mind before you started. At least that makes sense to me LOL