This is also good for painting some furniture. Use in the same rooms as the semi-gloss. Most jobs require two coats of paint. A gallon of paint will be good for doing a room. If you're just painting shelves or furniture, a liter should do.
Paint always dries darker than it appears going on.
Depending on the project you want to do you might be able to get away with using craft paints or testers. Any hobby or craft store will sell 2-oz bottles of craft paint. Also available in craft-paint size is a varnish, which is good for small projects, but it's cheaper to buy a large can if you have more than one project. If you are painting on unfinished wood, you will need to first paint a coat of primer on the wood. Primer seals your wood and gets it ready to take the paint.