Will you be buying yarn from a yarn store or from a large chain like Michael's or Walmart?

If you are buying from a local yarn store, which is what I recommend, you can get just about anything with out going wrong. There are many skiens that are under $10 that will complete a whole project. If you get cascade 220 you can make a scarf or hat and then felt it. I like getting blended yarn. Jo Sharp is one of my favorites.

If you are buying from a large chain, which I don't recommend unless absolutely necessary, I would stay away from shiny acrylic yarn. It can look pretty, but it does not stay looking pretty over time. I would try to find something with wool, cotton, or silk in it. If any of those are blended with the acryic it can help the scarf look nicer longer.

I learned these lessons the hard way. I made scarves, hats, fingerless gloves, and purses out of the shiny soft 100% acrylic yarn thinking it would stay nice looking. Unfortunately after a few months the project starts looking ratty, fuzzy and sad.

I really like Colour 4 Me by Shepherd. It is carried at most local yarn shops and comes in a lot of colors: www.shepherdyarns.biz/Yarn/colour_me.htm It is a soft yarn, even soft enough for babies, and wears well. I've used it for anything from baby clothing to men's hats.

Salihah