If you could only buy one baby carrier, what would it be

[onthefly]

A ring sling is a good option. It's good for newborns through to toddlers (for quick hip carries).
A manduca or similar is also a good one as it's easy and accessible and can be used from newborn through. I wouldn't go with an ergo just because they don't carry from newborn - you need a separate insert for that.

i prefer woven wraps and they're truly the most versatile but they can seem a bit daunting at first

[onthefly]

and Just FYI about Ergo fakes. There are a lot around and the trouble with them is that you can't be sure about the materials or workmanship, or whether they've been properly tested.
If you're unsure, you can check registered ergobaby stockists via the Babes in Arms website.