If I was to check some local thrift shops for some inexpensive shirts, pants and jackets what should I look for that would be good matierial for backpacking and hiking? I know cotton is no good. I guess wool is good but all I know about wool is some itchy sweaters I had as a kid. Is silk good material? What about fleece, is it all polyester and is it good, or what should I be looking for.

Will be taking two overnight hike/BP trips with the kids soon, and it will probably be cool to freezing. We have a great goodwill thrift shop that I'm sure has some items that would be great, if I only knew what to look for! Thanks for any advice!