I sewed for the first time in December 2009. New Brother machine.
I'm sorry to sound negative, but you have to assume that you will screw up one or two items. That is part of the learning process. So, I highly recommend that you start with a simple pattern and some cheap fabric. Once you have your basics mastered, you can move toward more complexity with high-tech fabrics.
I started with stuff sacks, then got a rain parka pattern. The first parka was kind of a mess, but the second one works fine. A bivvy sack is easy. A silk sleeping bag liner is useful.