To what extent did the ideology of classical liberalism contribute to the common good?

It contributed a lot to the common good. Keep in mind that what is today called classical liberalism, or libertarianism is not the same thing as what is used in the US and some other countries as 'liberalism' the two ideologies could not be further apart.

Classic Liberalism helped the common good by removing artificial barriers. This included artificial barriers to trade (for example, rather than everyone being able to trade with everyone else, a single government-sponsored monopoly would be the only one to trade with certain people, countries or with certain goods) this helped lower prices with competition so the average person could afford more goods like clothing and food. It also included artificial barriers to life itself, a person no longer was pressured or forced to believe a certain way and so people were free to choose their own religion, a person also was no longer pressured to paint the ruling elite in a favourable light, instead they could use the freedom of the press to show corruption in the ruling class. It also helped protect minorities and dissidents by limiting the government to only have the power to intervene in specific instances so even with a majority vote they couldn't harm the minority.