What does Jeannette's fascination with watches represent in The Glass Castle?

Jeannette writes,

Unlike diamonds, watches were practical. They were for people on the run, people with appointments to keep and schedules to meet.

The watch symbolizes the life Jeannette longs for and the goals she has for herself. In its practicality, she sees the hope of a future when she isn't on the run simply because her father needs to make another escape, but because she has obligations and responsibilities. She longs to become self-sufficient and to live a life completely unlike that of her childhood, when even her most cherished possessions are given away by her parents. Watches, especially higher-end ones, signify a certain amount of wealth that her family doesn't have the luxury to afford.
Jeannette sees the watch as a physical representation of the gap between her family's history and the sustainability she aspires to have when she doesn't have to rely on the completely unpredictable and inexplicable choices her parents force on the children throughout their childhoods, always grounding them in a life of poverty.