Sewing knits is not really that bad. Follow the ideas suggested by Grama and Bear and you will be fine. I made all of my daughter's pants when she was young because she was so skinny, nothing fit. There are tons of great patterns and fabrics out there.
In answer to your question about stretch requirements, look on the pattern envelope. You should see a bar that says something like "a four inch piece of fabric should stretch to here". That is the stretch gauge.