You might be tempted to run out and buy all sorts of cute school furniture, but don't. If you have extra money, spend it on supplies, not furniture. The supplies needed are the types of things you probably already have around. The most important supplies are for the art department of your school. Nothing you do besides reading together will do more to give your child the necessary skills for school.
Art develops small motor skills, intelligence and creativity.
You almost can't have too many art supplies, but they don't have to be expensive. I mean the things you have around your house that don't look artistic to you, but do look artistic to children. Just collect a big box of the stuff and set it with your supplies. Story-telling materials are also important. Puppets are easy and inexpensive to make.