Dresses
There have been questions about what the formal gown should look like. First I will say, make whatever you want. But making a true pageanting gown will likely get you more points as it will involve more detail and skill.
To start, the difference between a pageant, or prom, dress and an evening gown/ red carpet gown is in the elegance. Pageant and prom gowns are not as elegant and can even be tacky. The key differences between prom and pageants gowns is summarized in this article. You can also visit this site for basic pageant tips and info. Basically, pageant gowns are better made and have more gilitz and glam. A pageant gown is designed to stand out on stage, not just in a room. A good pageant gown flatters the wearer, while expressing her personality at the same time. Think about creativity, not just making something generic.Some Examples:
You can see that the evening gown/ red carpet gown is much simpler but more elegant. The pageant gown is not as elegant as the evening gown, but it is considerable more detailed. The pageant gown is simpler and not as well made.
These are a couple of good sites with pageant gowns, but just typing "pageant gown" into Google works also:
Link 1 -- Link 2 -- Link3 -- Link 4
Disclaimer -- These are broad generalizations, most of my pageanting knowledge comes from being a competative dancer and knowing people who have participated in pageants. There is a wide range of quality in all dresses, but as there is no real cost here your doll should have the best and the most fitting for the pageant.