Every Monday I have a infographic about basic sewing to answer one of your questions. Feel free to ask questions in the comments or email me. Also, if you know the answer to someone's question, go ahead and answer it. We're here to help each other learn about sewing!
My thoughts on a serger are get a nice expensive sewing machine and then get a cheaper serger because you always need a sewing machine, but you can technically live without a serger. Unless you are going to use it constantly or you have a home sewing business. Also, my sewing professor had 5 spool sergers that could change to do a coverstitch. She said she would have rather gotten a different machine to do a coverstitch because it was such a big ordeal to change the machine.