The Prince was looking over the city noticing how deprived he was of the truth: That while he was Prince and rich, the people of lesser birth died of hunger and disease in poverty at the slums. Hence, the Prince wanted to sacrifice himself and somehow give back to all of those he was unable to reach, and help. As a statue, he was made of gold, so he asked that he (in an allegorical relationship to self-punishment) is peeled off his leaves of gold.
However, in a sarcastic tone, Wilde also he implies that gold is the only element of happiness in the world, according to the people. At that time, Wilde was claiming to be a Socialist (he was shifty with his beliefs and switched back and forth) so during this period of his life, he sort of took digs at Capitalism. Therefore, Wilde uses gold as a symbol of avarice (the same avarice that once covered the Prince) and how, because of avarice, many have to sacrifice and suffer, at times even until their deaths.
Ultimately, that gold (now in its normal meaning) will be peeled off the Prince to make others happy the same way that many have sacrificed the happiness of people just for the sake of money.