Most cloth diaper accessories are not necessary, but they sure do make cloth diapering easier. I know that I wouldn't attempt cloth diapering without most of these. Here are some things you might want to consider.
Diaper Pail Liner - A reusable waterproof pail liner for your diaper pail. It has PUL on the inside and fabric on the outside. When it is laundry day I simply lift the liner out of the pail, dump the contents into the washing machine, throw in the pail liner, and wash everything at once. I would recommend buying two so you always have one for your dirty diapers while the other is in the wash.
Diaper Sprayer - Once your child starts solids or if they are formula fed you may want to think about getting a diaper sprayer. For some sprayers are a luxury, but if you ask me they are essential. It ensures that I keep my hands clean when dealing with poopy diapers. You also do not need to buy an expensive sprayer that is marked for cloth diaper use. We bought a simple kitchen sprayer and hooked it to our toilet. According to my husband it was a simple install, but I have a feeling he had a chat with some of the workers at the hardware store first.