A few parents have asked for suggestions on iPad styluses to buy. They are not needed for most apps, but you or your child may find them useful or engaging for certain activities. The Apple brand styluses are good but quite expensive, but there are many less expensive options on the market - the hard thing is picking one.
An article in this week's Wirecutter has a recommendation gives a good overview of purchase considerations and the competition and has a recommendation for one that is $10.