There are two kinds of orthodontics, one is wire orthodontics, which uses external force to pull your root, and the time depends on the development of your alveolar bone. The sooner you do it, the better, usually 1 to 2 years. It can be divided into traditional steel wire brackets, ceramic brackets and invisible orthodontics without brackets, and the cost depends on the complexity of teeth. Generally it is about 3000 to 10000.
At present, the correction of beauty crowns is only for adults, and only a few ugly teeth' enamel with different materials have been made in a short time. The cost is usually 300 to 3000 yuan per capsule.
Adults can do both options, walking a tightrope is to do the whole mouth, and the beauty crown is only to do your bad teeth. Ask several hospitals to see which one is suitable for you.
I hope it works for you!