What makes for a good marriage in the novel?
It may depend on whose perspective.
On Chapter 4 we find out that Anne had met CPT Wentworth in the Summer of 1806, fell in love with him, and he proposed to her. By this time, she had based her idea that a good marriage depends on nothing but love. Support and affection are part of that love. Money and titles meant nothing to her. For this reason, Anne would arguably agree that it would have been a good marriage.
Yet, Lady Russell had other plans. She knew how vain Anne's father was, and that he was a snob. She also knew that Anne's family was in need of financial back up, and she truly felt that Anne deserved a life of carefree comforts. Hence, bringing Anne's father as the primary reason, she explained to Anne that a marriage to a man who is not rich, nor socially classed, would be tedious, imprudent and impractical.
Therefore, the idea behind making a "good marriage" in the novel is precisely finding someone of higher ranking and richer means to start a family that would enjoy the pleasures of a developing society, especially that of London which was to become the most fashionable and richest city in the world.
Anne was persuaded not because she wanted to make that kind of good marriage, but because she wanted to please her father, which was a must in her time and age. She was also naive, and too young to understand the consequences. When she was proposed to again by another man of better means, she refused him, going back to her assertion that a good marriage should involve love. She never stopped loving Wentworth, and she suffered dearly for allowing Lady Russell to butt in.