Start small…stuff sacks/pillows and the like. Cheap and stable materials like cotton to begin. Rip up old clothes and just get a feel for the machine and the craft. Try sewing one old t-shirt on top of another, or cut one up to make patches and sew it to another for starters. Learn the nuances of that particular machine; how it feels, how it jams, comes apart, changing threads, starting/stopping seams, etc.
Make some small clothes/blankets/whatever for a kid's center (new cloth) and donate your handicrafts. They may not be commercial quality but they're much better than nothing and a better use than just throwing projects away or having them sit in a closet. Even "doll clothes" are hugely appreciated by the kids and help with the fine detail-work and working in small spaces.
Scale up from there into the more expensive materials. When you move to a new material, again, go back to small things until you see how that material "behaves."
The more you can do 'with a purpose to give away' the easier it is to stick with it because it's less about what you're getting out of it and more about the craft itself.
Also, people love gifts and it's fun to give stuff away. :)
-mox