Any kind of lightly padded ring sling will be fine for you. They are sold in sizes... I'm plus sized (wear about a size 18) and about 6 foot. I have an ella-Roo lightly padded ring sling in a large. Reece is about 15-16 lbs right now and I can still wear him in it for hours on end. Although, I find the front Kangaroo carry a bit too much for my back these days. But anything that ties him flat to me on my hip or front is PERFECT. The Ella Roo fabric is a rather heavy cotton... I wear Reece outside here (we live in northern Ontario, it's cold lol) but I line the sling w/ a fleece blanket, then Zip him into my jacket and put a hat on him... If it's windy I just use the sling tail to toss over his head to protect his face. There are also jacket or vest options that are made for baby wearing in cold climates.
You can also get mesh slings for summer, very light and made to wear baby in the heat... But you wouldn't want to use it in cool weather. But a cotton sling can be used year round for the most part so IMO, cotton or hemp is a better option if you only want to get 1 sling.
But... You don't have to get the Ella Roo either, there are sooo many slings on the market. I would look for something that opens up nice and wide across your shoulder and back (some will have a rather narrow shoulder/back area and that can be uncomfortable as baby get older a wide lightly padded shoulder and wide back helps disperse weight and pressure REALLY well), something lightly padded along the rails (I find it helps from any slipping through the rings) and stay away from silk or other delicate fabrics and something with a really long dramatic tail for your 1st sling. And you may want to make sure the fabric of the sling is comfortable.. Some slings (even the Maya) are made of a rough fabric and you may not want that for a new baby... The Way Reece likes to be tied meant that he had that rough fabric around the back of his neck or cheek (not nice

).... Once you have the sling thing figured out, then go crazy picking out beautiful fabrics or whatever
Here is a link w/ every possible sling that I can think of....
http://store.attachedtobaby.com/sear...x?categoryid=3
HTH!