All dragons love gold. But the root of this love is more than just fascination, it is the source of all your power. As you collect gold your dragon will increase in power level and size.
This will be most significant resource and will be earned by killing denizens and their dwellings. The cities and the travelers between them will need to be “liberated” of their gold burden so you can gain power. To best leverage resource acquisition, you will need to prioritize your attacks to maximize your power growth.
Of course, other dragons also have significant gold you could take... if you can defeat them.