First, see if you have a babywearing group in your area. Check meetup.com and yahoo groups. They usually meet once a month and you can go and try out other mama's slings, get recommendations, and sometimes get them used from each other. Here is a good website for help too: http://www.thebabywearer.com/
Moby and mei tai are pretty different. I have an ergo, but it is bulky. I have used a mei tai, and plan to get one with next baby early on. I have a moby and I like it, but it is not good for higher weights. It is great for snuggling with infants and getting stuff done around the house. I think it is more comfy than a mei tai, but that might have been because my son was bigger when I used the mei tai. It is not convenient for out in public with all the wrapping that it needs. It can be hot for running errands too. Mei tai is more convenient and good for longer term. It's easy to put on, not too big and bulky, still holds baby close and can do skin-to-skin time in it. I haven't nursed in it so I can't tell you about that part, and I didn't use it with a newborn.
I bought cheap fabric and tried to make my own moby and it was a waste of time- too stretchy and unsupportive. I read all about people doing it, but by the time you buy several yards of quality jersey fabric it is just as expensive as a new one. If you can find one on ebay or otherwise used, go for it, you can wash it. Make sure it is a reputable seller so it isn't too worn or stretched out would be my only concern.
Making my own mei tai was not an option, I don't have the sewing skills necessary for that. I would think you would need a heavy duty machine to be able to go through multiple layers of sturdy fabric and I don't have one. I didn't trust anything I was able to sew to be able to hold up to baby's weight. I'm sure if you can sew and have the necessary equipment it wouldn't be hard. They are more expensive so it might be cost-effective where the moby is not, but I don't really know.
Hope all that helps!
***ADDED***
I knew I should have just posted this info to begin with, but was trying to keep it shorter. In response to the other post, yes certain types of baby slings were recalled and are dangerous. I read this article a long time ago when looking at slings. It explains the difference between the recalled type and a hotsling/peanut shell pouch type pretty well. The reason for the recall was that baby's head gets forced down toward their chest in the bag sling, cutting off their airway and they suffocate. A pouch sling positions baby differently. Babywearing is something that should be done with a little bit of knowledge and safety should be kept in mind. You don't just stuff baby in a pouch and go.
http://www.babyslingsafety.blogspot.com/