Some people do very well with gEDA. Other swear by Kicad...if you plan to design real PCBs in the future, your time would be better spent learning some other tool.
Ah. The latter comment is WRT "Fritzing"; I spent a while trying to figure out why someone was bad-mouthing gEDA and KiCAD.
There are certain concepts in common with a lot of CAD packages. EAGLE, gEDA, and KiCAD will all teach you some of those concepts. Fritzing... probably not. It'd be like learning APL as your first computer language!