I chose the Singer Heavy Duty 4423 - not too fancy. The 4452 offers many more stitch options but I wasn't sure if I was even going to like sewing. Obviously I realize now I would've appreciated the better one!
This machine has been great for me though. The heavy duty series has 1,100 stitches/minute compared to about 800/minute normally. It's also strong enough to chew through heavy fabrics -which is handy for patching my husband's work pants and jeans. It was easy to install a walking foot for sewing knits too. What I like about heavy duty series is that it's very common - so there's videos all over youtube to help you learn how to change the feet, oil it and use it! I was a true beginner so I relied on the internet a lot. No shame there!
Now that I'm an "advanced beginner", I've bought myself some fun toys!
I have a Brother 1034d. This machine has a facebook group entirely dedicated to it! You can have your questions answered any time of day or night. If you've never used a serger, you're missing out. It's SO FAST! A serger uses up to four threads at a time and cuts the seam allowance off, giving you the strong professional seam you're used to seeing - there's example photos below.
I have a Brother 2340CV cover stitch. This machine also uses up to four threads, but it doesn't have a blade like a serger. It makes the really clean twin needle-looking hem you're used to seeing on store bought clothes. It has a looper on the bottom which tucks in the seam allowance so it won't fray.
If you're sewing with a woven fabric (not-stretchy) then your pattern directions likely tell you to press the hem 1/4" and sew, then press the hem another 1/4" and sew again. This is so the edge is enclosed and cannot fray. With a cover stitch you could skip this step - just fold 1/2" and cover stitch! The edge would be enclosed by the looper. This machine can also do a decorative stitch known as a "flat lock". Sample photos below.
I didn't buy any extra feet or any other accessories for my serger or my coverstitch. I haven't found that I needed them. The machines were ready to use, right out of the box!
For both machines I use Maxi-lock stretch thread. Because it stretches, you won't hear your seams rip when you pull the shirt over your head. If you can't swing stretch thread for all four cones, you could get away with just having it in the loopers of each machine and using regular Maxi-lock in the needles (it's a little cheaper). Beware of discount thread! It will leave fuzz all over the inside of your machine. If you've invested in specialty machines like these, you'll want to take care of them (and probably name them).
Be sure to oil your serger before first use. You can use the same oil you use on your sewing machine. The coverstitch does not require oiling.
Also be sure to clean dust out of the presser foot areas. A lot of people use compressed air but I feel like this just blows the dust further into the machine where I can't get to it. I use a keyboard vacuum.
Selecting a machine
How did I decide on my serger and coverstitch? I read reviews, listened to a lot of online chatter and squinted at facebook videos to see what kind of machines the sewing internet celebrities have on their tables. I was surprised to find that Megan of Made for Mermaids and Judy of Patterns for Pirates each have both of these machines. I was surprised because these are actually the cheapest in their categories - obviously that's not holding the pros back, so I have no need for anything fancier. I'm really happy with both machines. And since my sewing room is also my living room, it helps that they're attractive.
This is the inside of a skirt sewn on a sewing machine. Notice that the seam allowance is not trimmed? A zig zag stitch just holds the fabric together.
This is what that seam would look like on a serger with four threads and the seam allowance clipped.
This is the ankle of a pair of pajama pants. I used a narrow zig zag stitch on a sewing machine - the inside and outside look the same.
This is what a hem looks like with a cover stitch with four threads. There are three rows of straight stitches on top and a looper that catches them all and the allowance on the inside.
A decorative flat lock stitch would be the opposite - where the looper is visible on the outside and the straight stitch is inside.