Hey there. I have one serger, and I just love it to death!! I have a Kenmore. When I told my husband I wanted one, he went nuts reading up on all kinds of forums and consumer reports about different brands and all. Together we learned so much about them before even buying one. Prices will from $300 to $3000 (which is up to your budget) threads can go from 3 spools to 10 ( I haven't figured those out yet). With my Kenmore the features I love so much are the suction cups on the feet to hold it to the table (these machines are fast and without those will bounce!!) the weight is nice and heavy, but I can easily pick it up to put it away. And it's easy to open to clean out.
When you do make a decision about one and purchase it. Play with it!!! I was scared to death to change the thread (mine came prethreaded) but if I did it, anyone can. Most of the forums will talk about people who buy an expensive serger, get scared of it and put in the box and back to the closet. After hearing that I was determined to learn how to use it! We have cats and I tried leaving my serger out and ready to use, but I noticed one cat actually chewing on the tread (I was not amused). Luckly, I had bought a good carrier for it, so when I'm not using it, I do put it away. We paid under $500 for mine, which does exactly what I was looking for. There are so many brands and features it all depends on what you want, but if you start off small you can always work your way up. Lots of shops will let you try them out...that's always a big plus. And buy a book, I found a wonderful book which is not specific to any one brand, she talks about everything from fears to different threads how to make each stitch look correctly.
Good luck and tell us what you end up getting!!