If you've never done it before, I'd suggest not starting out too big, before really being certain that your interest in the hobby will take, lest you wind up with a machine that you lose money on after it collects dust in a closet for a year and is eventually sold on craigslist.
I'm not a MD Guru, but I do know a great entry level machine is the Tesoro Compadre. I'm actually in the process of buying a second one to keep as a backup at home in FL. They are *dead simple* to use, have a lifetime warranty (which speaks to the fact that they're reliable as anvils), cost about $150 shipped and on small gold, perform as good as pretty much any machine, regardless of price.
If you buy one and decide that MD'ing is for you, you can step up to whatever you want, but really, you will still find find yourself using that simple and ultralight Tesoro, even when you own more expensive machines.
I liken my Compadre to this old Stevens 12 gauge side by side shotgun I had.
I owned a lot of other shotguns, including a couple over/unders that were pretty spendy, but when I found myself heading out into the woods to bust a few birds, I always seemed to grab that thing. Wasn't the most 'impressive' machine I owned, but it was the one I wound up using an awful lot.