Start with an A-line skirt. I prefer ones with waistbands, rather than those waist-bandless facing things that you find in RTW.

I think waistbands are easier, sit better, and are more comfortable, but opinions on that are divided. My favorite generic skirt pattern is this one, by Butterick (http://www.butterick.com/item/B3134.htm??tab=list/skirts_pants&page=all). I've made probably a dozen skirts from that one pattern. No kidding. Great pattern!