I love my serger and use it on a wide variety of projects. It does take some effort before it becomes an easy tool to use. If you are willing to spend the time, maybe take some lessons from a local sewing shop I would get one in a heart beat. You can teach yourself using on line tutorials or videos, it's just so much easier for me when I have my hands on it and a teacher working directly with me.
That said....when I bought mine, a used Juki Pearline, I called the place where I bought my sewing machine and talked to their repair person and a sales person. They gave me lots of great advice about questions to ask and things to look for when I test drove it. I was really fortunate and got a real gem of a machine and for a really great price. Good luck.