When it comes to saving money, what is a good rule of thumb?

-Not to make impulse buys
-Open a savings account that directly adds a set amount of money into it from your paycheck monthly 
-The '50-30-20' rule(50 percent of your income toward necessities, like housing and bills. Twenty percent should then go toward financial goals, like paying off debt or saving for retirement. Finally, thirty percent of your income can be allocated to wants, like dining or entertainment.)
-Create a budget 

Your income should be greater than you're spending. So basically, don't spend more than you have. :)

Her interest would be the first to attract her to read the book then would come connection with the character which would keep her interest in the book.